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 $69.30   9.289%   $75.7373   $75.74   $75.75   $75.70  
  Purchase #2 $191.27   7.517%   $205.6478   $205.65   $205.65   $205.60  
  Purchase #3 $212.65   11.386%   $236.8623   $236.86   $236.85   $236.90  
  Purchase #4 $65.50   13.861%   $74.579   $74.58   $74.60   $74.60  
  Purchase #5 $203.86   8.871%   $221.9444   $221.94   $221.95   $221.90  
  Purchase #6 $68.53   7.535%   $73.6937   $73.69   $73.70   $73.70  
  Purchase #7 $132.74   10.556%   $146.752   $146.75   $146.75   $146.80  
  7 purchase totals = $943.85       $1,035.2165   $1,035.21   $1,035.25   $1,035.20