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 $241.82   10.746%   $267.806   $267.81   $267.80   $267.80  
  Purchase #2 $40.37   10.503%   $44.6101   $44.61   $44.60   $44.60  
  Purchase #3 $154.26   13.617%   $175.2656   $175.27   $175.25   $175.30  
  Purchase #4 $233.31   4.664%   $244.1916   $244.19   $244.20   $244.20  
  Purchase #5 $201.60   5.250%   $212.184   $212.18   $212.20   $212.20  
  Purchase #6 $231.43   6.872%   $247.3339   $247.33   $247.35   $247.30  
  Purchase #7 $167.85   5.400%   $176.9139   $176.91   $176.90   $176.90  
  7 purchase totals = $1,270.64       $1,368.3051   $1,368.30   $1,368.30   $1,368.30