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 $244.85   5.472%   $258.2482   $258.25   $258.25   $258.20  
  Purchase #2 $185.87   10.571%   $205.5183   $205.52   $205.50   $205.50  
  Purchase #3 $198.94   5.478%   $209.8379   $209.84   $209.85   $209.80  
  Purchase #4 $170.30   5.727%   $180.0531   $180.05   $180.05   $180.10  
  Purchase #5 $10.79   6.241%   $11.4634   $11.46   $11.45   $11.50  
  Purchase #6 $195.52   13.753%   $222.4099   $222.41   $222.40   $222.40  
  Purchase #7 $67.25   11.790%   $75.1788   $75.18   $75.20   $75.20  
  7 purchase totals = $1,073.52       $1,162.7096   $1,162.71   $1,162.70   $1,162.70