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 $208.58   7.751%   $224.747   $224.75   $224.75   $224.70  
  Purchase #2 $248.32   5.572%   $262.1564   $262.16   $262.15   $262.20  
  Purchase #3 $93.42   8.710%   $101.5569   $101.56   $101.55   $101.60  
  Purchase #4 $39.29   9.357%   $42.9664   $42.97   $42.95   $43.00  
  Purchase #5 $227.81   13.460%   $258.4732   $258.47   $258.45   $258.50  
  Purchase #6 $10.55   10.107%   $11.6163   $11.62   $11.60   $11.60  
  Purchase #7 $45.47   11.753%   $50.8141   $50.81   $50.80   $50.80  
  7 purchase totals = $873.44       $952.3303   $952.34   $952.25   $952.40