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 $88.28   8.670%   $95.9339   $95.93   $95.95   $95.90  
  Purchase #2 $234.62   4.340%   $244.8025   $244.80   $244.80   $244.80  
  Purchase #3 $136.29   5.438%   $143.7015   $143.70   $143.70   $143.70  
  Purchase #4 $162.31   4.526%   $169.6562   $169.66   $169.65   $169.70  
  Purchase #5 $8.27   6.453%   $8.8037   $8.80   $8.80   $8.80  
  Purchase #6 $215.88   8.718%   $234.7004   $234.70   $234.70   $234.70  
  Purchase #7 $240.79   12.759%   $271.5124   $271.51   $271.50   $271.50  
  7 purchase totals = $1,086.44       $1,169.1106   $1,169.10   $1,169.10   $1,169.10