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 $183.97   6.420%   $195.7809   $195.78   $195.80   $195.80  
  Purchase #2 $84.46   9.749%   $92.694   $92.69   $92.70   $92.70  
  Purchase #3 $16.79   13.356%   $19.0325   $19.03   $19.05   $19.00  
  Purchase #4 $183.78   5.227%   $193.3862   $193.39   $193.40   $193.40  
  Purchase #5 $60.59   11.142%   $67.3409   $67.34   $67.35   $67.30  
  Purchase #6 $151.71   9.653%   $166.3546   $166.35   $166.35   $166.40  
  Purchase #7 $20.25   11.274%   $22.533   $22.53   $22.55   $22.50  
  7 purchase totals = $701.55       $757.1221   $757.11   $757.20   $757.10