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 $119.82   5.310%   $126.1824   $126.18   $126.20   $126.20  
  Purchase #2 $127.83   6.338%   $135.9319   $135.93   $135.95   $135.90  
  Purchase #3 $120.95   6.607%   $128.9412   $128.94   $128.95   $128.90  
  Purchase #4 $237.73   7.448%   $255.4361   $255.44   $255.45   $255.40  
  Purchase #5 $112.70   3.174%   $116.2771   $116.28   $116.30   $116.30  
  Purchase #6 $148.89   3.227%   $153.6947   $153.69   $153.70   $153.70  
  Purchase #7 $171.28   4.610%   $179.176   $179.18   $179.20   $179.20  
  7 purchase totals = $1,039.20       $1,095.6394   $1,095.64   $1,095.75   $1,095.60