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 $55.46   6.392%   $59.005   $59.01   $59.00   $59.00  
  Purchase #2 $46.79   4.393%   $48.8455   $48.85   $48.85   $48.80  
  Purchase #3 $194.69   5.562%   $205.5187   $205.52   $205.50   $205.50  
  Purchase #4 $210.61   12.633%   $237.2164   $237.22   $237.20   $237.20  
  Purchase #5 $97.65   7.844%   $105.3097   $105.31   $105.30   $105.30  
  Purchase #6 $184.33   8.357%   $199.7345   $199.73   $199.75   $199.70  
  Purchase #7 $176.66   10.468%   $195.1528   $195.15   $195.15   $195.20  
  7 purchase totals = $966.19       $1,050.7826   $1,050.79   $1,050.75   $1,050.70