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 $101.71   5.740%   $107.5482   $107.55   $107.55   $107.50  
  Purchase #2 $205.83   13.492%   $233.6006   $233.60   $233.60   $233.60  
  Purchase #3 $233.77   4.446%   $244.1634   $244.16   $244.15   $244.20  
  Purchase #4 $74.60   10.226%   $82.2286   $82.23   $82.25   $82.20  
  Purchase #5 $228.92   10.777%   $253.5907   $253.59   $253.60   $253.60  
  Purchase #6 $141.74   10.237%   $156.2499   $156.25   $156.25   $156.20  
  Purchase #7 $26.73   9.507%   $29.2712   $29.27   $29.25   $29.30  
  7 purchase totals = $1,013.30       $1,106.6526   $1,106.65   $1,106.65   $1,106.60