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 $58.42   5.616%   $61.7009   $61.70   $61.70   $61.70  
  Purchase #2 $245.93   8.573%   $267.0136   $267.01   $267.00   $267.00  
  Purchase #3 $217.46   7.799%   $234.4197   $234.42   $234.40   $234.40  
  Purchase #4 $94.56   5.178%   $99.4563   $99.46   $99.45   $99.50  
  Purchase #5 $208.57   11.569%   $232.6995   $232.70   $232.70   $232.70  
  Purchase #6 $26.74   11.779%   $29.8897   $29.89   $29.90   $29.90  
  Purchase #7 $32.90   9.754%   $36.1091   $36.11   $36.10   $36.10  
  7 purchase totals = $884.58       $961.2888   $961.29   $961.25   $961.30