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 $196.48   6.511%   $209.2728   $209.27   $209.25   $209.30  
  Purchase #2 $88.39   11.507%   $98.561   $98.56   $98.55   $98.60  
  Purchase #3 $87.95   8.335%   $95.2806   $95.28   $95.30   $95.30  
  Purchase #4 $248.72   9.722%   $272.9006   $272.90   $272.90   $272.90  
  Purchase #5 $114.67   4.629%   $119.9781   $119.98   $120.00   $120.00  
  Purchase #6 $155.73   3.264%   $160.813   $160.81   $160.80   $160.80  
  Purchase #7 $149.49   7.242%   $160.3161   $160.32   $160.30   $160.30  
  7 purchase totals = $1,041.43       $1,117.1222   $1,117.12   $1,117.10   $1,117.20