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 $214.96   10.139%   $236.7548   $236.75   $236.75   $236.80  
  Purchase #2 $181.87   11.182%   $202.2067   $202.21   $202.20   $202.20  
  Purchase #3 $145.84   3.811%   $151.398   $151.40   $151.40   $151.40  
  Purchase #4 $164.68   10.633%   $182.1904   $182.19   $182.20   $182.20  
  Purchase #5 $151.34   9.538%   $165.7748   $165.77   $165.75   $165.80  
  Purchase #6 $210.38   3.779%   $218.3303   $218.33   $218.35   $218.30  
  Purchase #7 $178.78   5.109%   $187.9139   $187.91   $187.90   $187.90  
  7 purchase totals = $1,247.85       $1,344.5689   $1,344.56   $1,344.55   $1,344.60