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 $67.84   8.496%   $73.6037   $73.60   $73.60   $73.60  
  Purchase #2 $214.37   10.266%   $236.3772   $236.38   $236.40   $236.40  
  Purchase #3 $238.91   11.485%   $266.3488   $266.35   $266.35   $266.30  
  Purchase #4 $69.50   9.159%   $75.8655   $75.87   $75.85   $75.90  
  Purchase #5 $188.49   7.623%   $202.8586   $202.86   $202.85   $202.90  
  Purchase #6 $105.96   12.216%   $118.9041   $118.90   $118.90   $118.90  
  Purchase #7 $53.68   12.722%   $60.5092   $60.51   $60.50   $60.50  
  7 purchase totals = $938.75       $1,034.4671   $1,034.47   $1,034.45   $1,034.50