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 $88.54   8.232%   $95.8286   $95.83   $95.85   $95.80  
  Purchase #2 $159.55   13.726%   $181.4498   $181.45   $181.45   $181.40  
  Purchase #3 $220.72   7.395%   $237.0422   $237.04   $237.05   $237.00  
  Purchase #4 $126.98   13.155%   $143.6842   $143.68   $143.70   $143.70  
  Purchase #5 $234.82   5.554%   $247.8619   $247.86   $247.85   $247.90  
  Purchase #6 $85.84   6.629%   $91.5303   $91.53   $91.55   $91.50  
  Purchase #7 $200.51   6.823%   $214.1908   $214.19   $214.20   $214.20  
  7 purchase totals = $1,116.96       $1,211.5878   $1,211.58   $1,211.65   $1,211.50