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 $94.87   12.174%   $106.4195   $106.42   $106.40   $106.40  
  Purchase #2 $211.81   7.182%   $227.0222   $227.02   $227.00   $227.00  
  Purchase #3 $90.50   4.844%   $94.8838   $94.88   $94.90   $94.90  
  Purchase #4 $250.80   8.811%   $272.898   $272.90   $272.90   $272.90  
  Purchase #5 $54.95   5.791%   $58.1322   $58.13   $58.15   $58.10  
  Purchase #6 $194.77   8.203%   $210.747   $210.75   $210.75   $210.70  
  Purchase #7 $177.26   5.289%   $186.6353   $186.64   $186.65   $186.60  
  7 purchase totals = $1,074.96       $1,156.7380   $1,156.74   $1,156.75   $1,156.60