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 $41.80   13.258%   $47.3418   $47.34   $47.35   $47.30  
  Purchase #2 $194.41   5.556%   $205.2114   $205.21   $205.20   $205.20  
  Purchase #3 $233.46   12.507%   $262.6588   $262.66   $262.65   $262.70  
  Purchase #4 $92.51   5.739%   $97.8191   $97.82   $97.80   $97.80  
  Purchase #5 $215.54   7.810%   $232.3737   $232.37   $232.35   $232.40  
  Purchase #6 $224.53   13.140%   $254.0332   $254.03   $254.05   $254.00  
  Purchase #7 $73.98   3.641%   $76.6736   $76.67   $76.65   $76.70  
  7 purchase totals = $1,076.23       $1,176.1116   $1,176.10   $1,176.05   $1,176.10