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 $116.39   8.774%   $126.6021   $126.60   $126.60   $126.60  
  Purchase #2 $195.32   4.789%   $204.6739   $204.67   $204.65   $204.70  
  Purchase #3 $219.83   9.632%   $241.004   $241.00   $241.00   $241.00  
  Purchase #4 $182.84   8.313%   $198.0395   $198.04   $198.05   $198.00  
  Purchase #5 $132.30   12.215%   $148.4604   $148.46   $148.45   $148.50  
  Purchase #6 $143.71   9.367%   $157.1713   $157.17   $157.15   $157.20  
  Purchase #7 $83.96   9.121%   $91.618   $91.62   $91.60   $91.60  
  7 purchase totals = $1,074.35       $1,167.5692   $1,167.56   $1,167.50   $1,167.60