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 $214.85   8.475%   $233.0585   $233.06   $233.05   $233.10  
  Purchase #2 $116.57   13.297%   $132.0703   $132.07   $132.05   $132.10  
  Purchase #3 $22.90   7.237%   $24.5573   $24.56   $24.55   $24.60  
  Purchase #4 $12.98   3.545%   $13.4401   $13.44   $13.45   $13.40  
  Purchase #5 $109.59   8.548%   $118.9578   $118.96   $118.95   $119.00  
  Purchase #6 $217.77   12.395%   $244.7626   $244.76   $244.75   $244.80  
  Purchase #7 $237.26   9.321%   $259.375   $259.38   $259.40   $259.40  
  7 purchase totals = $931.92       $1,026.2216   $1,026.23   $1,026.20   $1,026.40