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 $86.96   8.143%   $94.0412   $94.04   $94.05   $94.00  
  Purchase #2 $36.66   13.513%   $41.6139   $41.61   $41.60   $41.60  
  Purchase #3 $62.58   4.229%   $65.2265   $65.23   $65.25   $65.20  
  Purchase #4 $153.41   6.860%   $163.9339   $163.93   $163.95   $163.90  
  Purchase #5 $123.52   7.481%   $132.7605   $132.76   $132.75   $132.80  
  Purchase #6 $150.67   7.762%   $162.365   $162.37   $162.35   $162.40  
  Purchase #7 $204.61   13.673%   $232.5863   $232.59   $232.60   $232.60  
  7 purchase totals = $818.41       $892.5273   $892.53   $892.55   $892.50