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 $202.58   8.158%   $219.1065   $219.11   $219.10   $219.10  
  Purchase #2 $233.41   9.591%   $255.7964   $255.80   $255.80   $255.80  
  Purchase #3 $170.36   13.315%   $193.0434   $193.04   $193.05   $193.00  
  Purchase #4 $92.53   4.426%   $96.6254   $96.63   $96.65   $96.60  
  Purchase #5 $67.42   9.276%   $73.6739   $73.67   $73.65   $73.70  
  Purchase #6 $60.26   11.827%   $67.387   $67.39   $67.40   $67.40  
  Purchase #7 $244.67   4.862%   $256.5659   $256.57   $256.55   $256.60  
  7 purchase totals = $1,071.23       $1,162.1985   $1,162.21   $1,162.20   $1,162.20