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 $43.81   9.614%   $48.0219   $48.02   $48.00   $48.00  
  Purchase #2 $201.98   12.785%   $227.8031   $227.80   $227.80   $227.80  
  Purchase #3 $77.43   6.293%   $82.3027   $82.30   $82.30   $82.30  
  Purchase #4 $225.68   7.121%   $241.7507   $241.75   $241.75   $241.80  
  Purchase #5 $119.95   11.818%   $134.1257   $134.13   $134.15   $134.10  
  Purchase #6 $114.95   3.507%   $118.9813   $118.98   $119.00   $119.00  
  Purchase #7 $230.84   5.159%   $242.749   $242.75   $242.75   $242.70  
  7 purchase totals = $1,014.64       $1,095.7344   $1,095.73   $1,095.75   $1,095.70