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 $245.28   6.268%   $260.6542   $260.65   $260.65   $260.70  
  Purchase #2 $46.52   6.494%   $49.541   $49.54   $49.55   $49.50  
  Purchase #3 $104.73   5.132%   $110.1047   $110.10   $110.10   $110.10  
  Purchase #4 $75.47   12.261%   $84.7234   $84.72   $84.70   $84.70  
  Purchase #5 $207.98   4.498%   $217.3349   $217.33   $217.35   $217.30  
  Purchase #6 $185.59   6.308%   $197.297   $197.30   $197.30   $197.30  
  Purchase #7 $40.28   13.867%   $45.8656   $45.87   $45.85   $45.90  
  7 purchase totals = $905.85       $965.5208   $965.51   $965.50   $965.50