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 $62.68   7.206%   $67.1967   $67.20   $67.20   $67.20  
  Purchase #2 $106.43   3.168%   $109.8017   $109.80   $109.80   $109.80  
  Purchase #3 $152.27   6.726%   $162.5117   $162.51   $162.50   $162.50  
  Purchase #4 $31.58   3.622%   $32.7238   $32.72   $32.70   $32.70  
  Purchase #5 $122.28   9.798%   $134.261   $134.26   $134.25   $134.30  
  Purchase #6 $149.48   8.219%   $161.7658   $161.77   $161.75   $161.80  
  Purchase #7 $128.67   6.657%   $137.2356   $137.24   $137.25   $137.20  
  7 purchase totals = $753.39       $805.4963   $805.50   $805.45   $805.50