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 $194.39   6.470%   $206.967   $206.97   $206.95   $207.00  
  Purchase #2 $68.92   4.479%   $72.0069   $72.01   $72.00   $72.00  
  Purchase #3 $218.65   7.422%   $234.8782   $234.88   $234.90   $234.90  
  Purchase #4 $102.25   13.733%   $116.292   $116.29   $116.30   $116.30  
  Purchase #5 $172.53   13.489%   $195.8026   $195.80   $195.80   $195.80  
  Purchase #6 $112.89   7.461%   $121.3127   $121.31   $121.30   $121.30  
  Purchase #7 $181.60   8.466%   $196.9743   $196.97   $196.95   $197.00  
  7 purchase totals = $1,051.23       $1,144.2337   $1,144.23   $1,144.20   $1,144.30