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 $115.26   9.297%   $125.9757   $125.98   $126.00   $126.00  
  Purchase #2 $241.79   4.266%   $252.1048   $252.10   $252.10   $252.10  
  Purchase #3 $15.98   13.825%   $18.1892   $18.19   $18.20   $18.20  
  Purchase #4 $168.94   6.328%   $179.6305   $179.63   $179.65   $179.60  
  Purchase #5 $178.45   6.755%   $190.5043   $190.50   $190.50   $190.50  
  Purchase #6 $34.28   9.164%   $37.4214   $37.42   $37.40   $37.40  
  Purchase #7 $81.31   12.811%   $91.7266   $91.73   $91.75   $91.70  
  7 purchase totals = $836.01       $895.5525   $895.55   $895.60   $895.50