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 $224.49   3.346%   $232.0014   $232.00   $232.00   $232.00  
  Purchase #2 $243.98   11.609%   $272.3036   $272.30   $272.30   $272.30  
  Purchase #3 $237.89   12.297%   $267.1433   $267.14   $267.15   $267.10  
  Purchase #4 $201.93   13.851%   $229.8993   $229.90   $229.90   $229.90  
  Purchase #5 $141.54   8.561%   $153.6572   $153.66   $153.65   $153.70  
  Purchase #6 $48.49   13.130%   $54.8567   $54.86   $54.85   $54.90  
  Purchase #7 $244.45   7.367%   $262.4586   $262.46   $262.45   $262.50  
  7 purchase totals = $1,342.77       $1,472.3201   $1,472.32   $1,472.30   $1,472.40