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 $89.89   5.707%   $95.02   $95.02   $95.00   $95.00  
  Purchase #2 $79.78   3.244%   $82.3681   $82.37   $82.35   $82.40  
  Purchase #3 $157.31   12.434%   $176.8699   $176.87   $176.85   $176.90  
  Purchase #4 $192.29   7.600%   $206.904   $206.90   $206.90   $206.90  
  Purchase #5 $119.65   5.601%   $126.3516   $126.35   $126.35   $126.40  
  Purchase #6 $197.30   5.356%   $207.8674   $207.87   $207.85   $207.90  
  Purchase #7 $107.35   8.444%   $116.4146   $116.41   $116.40   $116.40  
  7 purchase totals = $943.57       $1,011.7956   $1,011.79   $1,011.70   $1,011.90