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 $61.87   4.775%   $64.8243   $64.82   $64.80   $64.80  
  Purchase #2 $105.42   7.720%   $113.5584   $113.56   $113.55   $113.60  
  Purchase #3 $107.77   9.135%   $117.6148   $117.61   $117.60   $117.60  
  Purchase #4 $228.95   7.590%   $246.3273   $246.33   $246.35   $246.30  
  Purchase #5 $244.70   13.251%   $277.1252   $277.13   $277.15   $277.10  
  Purchase #6 $169.86   10.495%   $187.6868   $187.69   $187.70   $187.70  
  Purchase #7 $76.33   13.833%   $86.8887   $86.89   $86.90   $86.90  
  7 purchase totals = $994.90       $1,094.0255   $1,094.03   $1,094.05   $1,094.00