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 $214.55   8.446%   $232.6709   $232.67   $232.65   $232.70  
  Purchase #2 $231.53   5.663%   $244.6415   $244.64   $244.65   $244.60  
  Purchase #3 $91.85   3.710%   $95.2576   $95.26   $95.25   $95.30  
  Purchase #4 $232.51   12.600%   $261.8063   $261.81   $261.80   $261.80  
  Purchase #5 $157.27   11.721%   $175.7036   $175.70   $175.70   $175.70  
  Purchase #6 $95.35   5.657%   $100.7439   $100.74   $100.75   $100.70  
  Purchase #7 $62.58   3.361%   $64.6833   $64.68   $64.70   $64.70  
  7 purchase totals = $1,085.64       $1,175.5071   $1,175.50   $1,175.50   $1,175.50