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 $32.51   5.466%   $34.287   $34.29   $34.30   $34.30  
  Purchase #2 $176.83   9.737%   $194.0479   $194.05   $194.05   $194.00  
  Purchase #3 $237.51   4.563%   $248.3476   $248.35   $248.35   $248.30  
  Purchase #4 $211.38   7.198%   $226.5951   $226.60   $226.60   $226.60  
  Purchase #5 $51.79   5.434%   $54.6043   $54.60   $54.60   $54.60  
  Purchase #6 $92.54   13.679%   $105.1985   $105.20   $105.20   $105.20  
  Purchase #7 $203.87   3.664%   $211.3398   $211.34   $211.35   $211.30  
  7 purchase totals = $1,006.43       $1,074.4202   $1,074.43   $1,074.45   $1,074.30