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 $219.51   11.441%   $244.6241   $244.62   $244.60   $244.60  
  Purchase #2 $118.73   11.452%   $132.327   $132.33   $132.35   $132.30  
  Purchase #3 $184.95   4.540%   $193.3467   $193.35   $193.35   $193.30  
  Purchase #4 $9.61   11.550%   $10.72   $10.72   $10.70   $10.70  
  Purchase #5 $228.86   3.374%   $236.5817   $236.58   $236.60   $236.60  
  Purchase #6 $212.79   13.113%   $240.6932   $240.69   $240.70   $240.70  
  Purchase #7 $97.39   5.165%   $102.4202   $102.42   $102.40   $102.40  
  7 purchase totals = $1,071.84       $1,160.7129   $1,160.71   $1,160.70   $1,160.60