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 $214.78   7.720%   $231.361   $231.36   $231.35   $231.40  
  Purchase #2 $61.79   10.301%   $68.155   $68.16   $68.15   $68.20  
  Purchase #3 $156.51   4.300%   $163.2399   $163.24   $163.25   $163.20  
  Purchase #4 $62.66   3.185%   $64.6557   $64.66   $64.65   $64.70  
  Purchase #5 $210.92   7.781%   $227.3317   $227.33   $227.35   $227.30  
  Purchase #6 $131.36   6.802%   $140.2951   $140.30   $140.30   $140.30  
  Purchase #7 $247.77   11.559%   $276.4097   $276.41   $276.40   $276.40  
  7 purchase totals = $1,085.79       $1,171.4481   $1,171.46   $1,171.45   $1,171.50