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 $124.51   7.363%   $133.6777   $133.68   $133.70   $133.70  
  Purchase #2 $174.49   12.780%   $196.7898   $196.79   $196.80   $196.80  
  Purchase #3 $245.32   11.657%   $273.917   $273.92   $273.90   $273.90  
  Purchase #4 $154.63   9.396%   $169.159   $169.16   $169.15   $169.20  
  Purchase #5 $41.35   4.674%   $43.2827   $43.28   $43.30   $43.30  
  Purchase #6 $235.53   8.557%   $255.6843   $255.68   $255.70   $255.70  
  Purchase #7 $240.60   8.381%   $260.7647   $260.76   $260.75   $260.80  
  7 purchase totals = $1,216.43       $1,333.2752   $1,333.27   $1,333.30   $1,333.40