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 $83.66   12.356%   $93.997   $94.00   $94.00   $94.00  
  Purchase #2 $109.73   3.154%   $113.1909   $113.19   $113.20   $113.20  
  Purchase #3 $189.63   3.534%   $196.3315   $196.33   $196.35   $196.30  
  Purchase #4 $36.32   5.340%   $38.2595   $38.26   $38.25   $38.30  
  Purchase #5 $104.87   10.684%   $116.0743   $116.07   $116.05   $116.10  
  Purchase #6 $152.54   11.808%   $170.5519   $170.55   $170.55   $170.60  
  Purchase #7 $249.50   5.740%   $263.8213   $263.82   $263.80   $263.80  
  7 purchase totals = $926.25       $992.2264   $992.22   $992.20   $992.30