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 $87.96   10.301%   $97.0208   $97.02   $97.00   $97.00  
  Purchase #2 $107.54   9.436%   $117.6875   $117.69   $117.70   $117.70  
  Purchase #3 $10.28   11.114%   $11.4225   $11.42   $11.40   $11.40  
  Purchase #4 $88.67   7.336%   $95.1748   $95.17   $95.15   $95.20  
  Purchase #5 $44.75   8.653%   $48.6222   $48.62   $48.60   $48.60  
  Purchase #6 $220.85   6.370%   $234.9181   $234.92   $234.90   $234.90  
  Purchase #7 $96.64   9.208%   $105.5386   $105.54   $105.55   $105.50  
  7 purchase totals = $656.69       $710.3845   $710.38   $710.30   $710.30