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 $194.95   10.711%   $215.8311   $215.83   $215.85   $215.80  
  Purchase #2 $220.38   3.337%   $227.7341   $227.73   $227.75   $227.70  
  Purchase #3 $89.75   7.751%   $96.7065   $96.71   $96.70   $96.70  
  Purchase #4 $161.71   3.415%   $167.2324   $167.23   $167.25   $167.20  
  Purchase #5 $197.37   3.627%   $204.5286   $204.53   $204.55   $204.50  
  Purchase #6 $189.92   9.605%   $208.1618   $208.16   $208.15   $208.20  
  Purchase #7 $19.79   11.324%   $22.031   $22.03   $22.05   $22.00  
  7 purchase totals = $1,073.87       $1,142.2255   $1,142.22   $1,142.30   $1,142.10