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 $83.41   5.444%   $87.9508   $87.95   $87.95   $88.00  
  Purchase #2 $119.61   6.313%   $127.161   $127.16   $127.15   $127.20  
  Purchase #3 $32.96   9.306%   $36.0273   $36.03   $36.05   $36.00  
  Purchase #4 $205.86   4.830%   $215.803   $215.80   $215.80   $215.80  
  Purchase #5 $166.65   6.561%   $177.5839   $177.58   $177.60   $177.60  
  Purchase #6 $10.66   8.212%   $11.5354   $11.54   $11.55   $11.50  
  Purchase #7 $162.39   3.261%   $167.6855   $167.69   $167.70   $167.70  
  7 purchase totals = $781.54       $823.7469   $823.75   $823.80   $823.80