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 $153.48   10.269%   $169.2409   $169.24   $169.25   $169.20  
  Purchase #2 $24.62   13.719%   $27.9976   $28.00   $28.00   $28.00  
  Purchase #3 $101.85   8.687%   $110.6977   $110.70   $110.70   $110.70  
  Purchase #4 $238.54   12.750%   $268.9539   $268.95   $268.95   $269.00  
  Purchase #5 $200.91   10.762%   $222.5319   $222.53   $222.55   $222.50  
  Purchase #6 $245.67   7.465%   $264.0093   $264.01   $264.00   $264.00  
  Purchase #7 $238.42   10.218%   $262.7818   $262.78   $262.80   $262.80  
  7 purchase totals = $1,203.49       $1,326.2131   $1,326.21   $1,326.25   $1,326.20