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 $110.78   3.623%   $114.7936   $114.79   $114.80   $114.80  
  Purchase #2 $13.66   4.518%   $14.2772   $14.28   $14.30   $14.30  
  Purchase #3 $36.87   9.292%   $40.296   $40.30   $40.30   $40.30  
  Purchase #4 $203.47   4.358%   $212.3372   $212.34   $212.35   $212.30  
  Purchase #5 $177.84   3.637%   $184.308   $184.31   $184.30   $184.30  
  Purchase #6 $151.40   6.872%   $161.8042   $161.80   $161.80   $161.80  
  Purchase #7 $101.26   6.515%   $107.8571   $107.86   $107.85   $107.90  
  7 purchase totals = $795.28       $835.6733   $835.68   $835.70   $835.70