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 $184.93   5.757%   $195.5764   $195.58   $195.60   $195.60  
  Purchase #2 $235.88   11.431%   $262.8434   $262.84   $262.85   $262.80  
  Purchase #3 $99.29   9.233%   $108.4574   $108.46   $108.45   $108.50  
  Purchase #4 $120.82   9.648%   $132.4767   $132.48   $132.50   $132.50  
  Purchase #5 $219.47   8.194%   $237.4534   $237.45   $237.45   $237.50  
  Purchase #6 $196.43   6.552%   $209.3001   $209.30   $209.30   $209.30  
  Purchase #7 $12.25   10.344%   $13.5171   $13.52   $13.50   $13.50  
  7 purchase totals = $1,069.07       $1,159.6245   $1,159.63   $1,159.65   $1,159.70