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 $85.41   11.457%   $95.1954   $95.20   $95.20   $95.20  
  Purchase #2 $170.54   4.307%   $177.8852   $177.89   $177.90   $177.90  
  Purchase #3 $233.27   3.386%   $241.1685   $241.17   $241.15   $241.20  
  Purchase #4 $180.49   7.148%   $193.3914   $193.39   $193.40   $193.40  
  Purchase #5 $86.88   7.298%   $93.2205   $93.22   $93.20   $93.20  
  Purchase #6 $176.73   10.550%   $195.375   $195.38   $195.40   $195.40  
  Purchase #7 $45.98   7.251%   $49.314   $49.31   $49.30   $49.30  
  7 purchase totals = $979.30       $1,045.5500   $1,045.56   $1,045.55   $1,045.60