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 $93.68   9.357%   $102.4456   $102.45   $102.45   $102.40  
  Purchase #2 $236.98   8.686%   $257.5641   $257.56   $257.55   $257.60  
  Purchase #3 $95.46   13.831%   $108.6631   $108.66   $108.65   $108.70  
  Purchase #4 $214.76   9.243%   $234.6103   $234.61   $234.60   $234.60  
  Purchase #5 $120.29   13.554%   $136.5941   $136.59   $136.60   $136.60  
  Purchase #6 $93.47   4.329%   $97.5163   $97.52   $97.50   $97.50  
  Purchase #7 $154.33   8.233%   $167.036   $167.04   $167.05   $167.00  
  7 purchase totals = $1,008.97       $1,104.4295   $1,104.43   $1,104.40   $1,104.40