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 $240.89   9.152%   $262.9363   $262.94   $262.95   $262.90  
  Purchase #2 $119.44   8.152%   $129.1767   $129.18   $129.20   $129.20  
  Purchase #3 $119.51   11.688%   $133.4783   $133.48   $133.50   $133.50  
  Purchase #4 $196.41   11.746%   $219.4803   $219.48   $219.50   $219.50  
  Purchase #5 $202.77   8.212%   $219.4215   $219.42   $219.40   $219.40  
  Purchase #6 $18.44   13.674%   $20.9615   $20.96   $20.95   $21.00  
  Purchase #7 $35.68   10.657%   $39.4824   $39.48   $39.50   $39.50  
  7 purchase totals = $933.14       $1,024.9370   $1,024.94   $1,025.00   $1,025.00