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 $215.77   4.287%   $225.0201   $225.02   $225.00   $225.00  
  Purchase #2 $105.26   11.475%   $117.3386   $117.34   $117.35   $117.30  
  Purchase #3 $142.51   7.750%   $153.5545   $153.55   $153.55   $153.60  
  Purchase #4 $155.95   5.237%   $164.1171   $164.12   $164.10   $164.10  
  Purchase #5 $232.43   5.419%   $245.0254   $245.03   $245.05   $245.00  
  Purchase #6 $192.47   12.297%   $216.138   $216.14   $216.15   $216.10  
  Purchase #7 $119.35   6.651%   $127.288   $127.29   $127.30   $127.30  
  7 purchase totals = $1,163.74       $1,248.4817   $1,248.49   $1,248.50   $1,248.40