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 $58.89   13.712%   $66.965   $66.97   $66.95   $67.00  
  Purchase #2 $29.28   9.628%   $32.0991   $32.10   $32.10   $32.10  
  Purchase #3 $115.60   9.743%   $126.8629   $126.86   $126.85   $126.90  
  Purchase #4 $173.81   7.401%   $186.6737   $186.67   $186.65   $186.70  
  Purchase #5 $194.63   3.478%   $201.3992   $201.40   $201.40   $201.40  
  Purchase #6 $215.31   11.431%   $239.9221   $239.92   $239.90   $239.90  
  Purchase #7 $167.53   6.373%   $178.2067   $178.21   $178.20   $178.20  
  7 purchase totals = $955.05       $1,032.1287   $1,032.13   $1,032.05   $1,032.20