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 $215.28   9.139%   $234.9544   $234.95   $234.95   $235.00  
  Purchase #2 $12.88   13.842%   $14.6628   $14.66   $14.65   $14.70  
  Purchase #3 $75.75   5.228%   $79.7102   $79.71   $79.70   $79.70  
  Purchase #4 $22.60   9.204%   $24.6801   $24.68   $24.70   $24.70  
  Purchase #5 $170.37   11.685%   $190.2777   $190.28   $190.30   $190.30  
  Purchase #6 $164.70   8.440%   $178.6007   $178.60   $178.60   $178.60  
  Purchase #7 $45.75   5.593%   $48.3088   $48.31   $48.30   $48.30  
  7 purchase totals = $707.33       $771.1947   $771.19   $771.20   $771.30