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 $32.49   5.120%   $34.1535   $34.15   $34.15   $34.20  
  Purchase #2 $247.63   6.348%   $263.3496   $263.35   $263.35   $263.30  
  Purchase #3 $117.84   13.276%   $133.4844   $133.48   $133.50   $133.50  
  Purchase #4 $190.98   5.455%   $201.398   $201.40   $201.40   $201.40  
  Purchase #5 $191.52   9.607%   $209.9193   $209.92   $209.90   $209.90  
  Purchase #6 $154.43   10.586%   $170.778   $170.78   $170.80   $170.80  
  Purchase #7 $143.82   11.479%   $160.3291   $160.33   $160.35   $160.30  
  7 purchase totals = $1,078.71       $1,173.4119   $1,173.41   $1,173.45   $1,173.40