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 $59.50   3.658%   $61.6765   $61.68   $61.70   $61.70  
  Purchase #2 $136.50   11.262%   $151.8726   $151.87   $151.85   $151.90  
  Purchase #3 $138.66   8.404%   $150.313   $150.31   $150.30   $150.30  
  Purchase #4 $234.26   3.573%   $242.6301   $242.63   $242.65   $242.60  
  Purchase #5 $32.74   9.827%   $35.9574   $35.96   $35.95   $36.00  
  Purchase #6 $195.38   7.477%   $209.9886   $209.99   $210.00   $210.00  
  Purchase #7 $205.85   11.781%   $230.1012   $230.10   $230.10   $230.10  
  7 purchase totals = $1,002.89       $1,082.5394   $1,082.54   $1,082.55   $1,082.60