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 $73.31   3.299%   $75.7285   $75.73   $75.75   $75.70  
  Purchase #2 $47.88   12.763%   $53.9909   $53.99   $54.00   $54.00  
  Purchase #3 $135.61   13.551%   $153.9865   $153.99   $154.00   $154.00  
  Purchase #4 $209.96   5.578%   $221.6716   $221.67   $221.65   $221.70  
  Purchase #5 $101.28   10.390%   $111.803   $111.80   $111.80   $111.80  
  Purchase #6 $214.85   6.823%   $229.5092   $229.51   $229.50   $229.50  
  Purchase #7 $237.41   9.370%   $259.6553   $259.66   $259.65   $259.70  
  7 purchase totals = $1,020.30       $1,106.3450   $1,106.35   $1,106.35   $1,106.40