Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $196.55   11.746%   $219.6368   $219.64   $219.65   $219.60  
  Purchase #2 $248.92   5.608%   $262.8794   $262.88   $262.90   $262.90  
  Purchase #3 $96.63   5.128%   $101.5852   $101.59   $101.60   $101.60  
  Purchase #4 $165.70   7.820%   $178.6577   $178.66   $178.65   $178.70  
  Purchase #5 $182.68   11.108%   $202.9721   $202.97   $202.95   $203.00  
  Purchase #6 $155.74   9.247%   $170.1413   $170.14   $170.15   $170.10  
  Purchase #7 $100.71   11.422%   $112.2131   $112.21   $112.20   $112.20  
  7 purchase totals = $1,146.93       $1,248.0856   $1,248.09   $1,248.10   $1,248.10