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 $60.26   6.369%   $64.098   $64.10   $64.10   $64.10  
  Purchase #2 $218.89   3.586%   $226.7394   $226.74   $226.75   $226.70  
  Purchase #3 $108.54   7.406%   $116.5785   $116.58   $116.60   $116.60  
  Purchase #4 $250.91   7.779%   $270.4283   $270.43   $270.45   $270.40  
  Purchase #5 $188.39   10.603%   $208.365   $208.37   $208.35   $208.40  
  Purchase #6 $15.60   6.117%   $16.5543   $16.55   $16.55   $16.60  
  Purchase #7 $194.47   4.826%   $203.8551   $203.86   $203.85   $203.90  
  7 purchase totals = $1,037.06       $1,106.6186   $1,106.63   $1,106.65   $1,106.70