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 $62.61   8.448%   $67.8993   $67.90   $67.90   $67.90  
  Purchase #2 $147.33   4.700%   $154.2545   $154.25   $154.25   $154.30  
  Purchase #3 $197.71   8.115%   $213.7542   $213.75   $213.75   $213.80  
  Purchase #4 $173.36   5.503%   $182.9   $182.90   $182.90   $182.90  
  Purchase #5 $61.82   7.297%   $66.331   $66.33   $66.35   $66.30  
  Purchase #6 $126.25   4.735%   $132.2279   $132.23   $132.25   $132.20  
  Purchase #7 $191.46   7.184%   $205.2145   $205.21   $205.20   $205.20  
  7 purchase totals = $960.54       $1,022.5814   $1,022.57   $1,022.60   $1,022.60