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 $62.73   12.673%   $70.6798   $70.68   $70.70   $70.70  
  Purchase #2 $201.83   6.473%   $214.8945   $214.89   $214.90   $214.90  
  Purchase #3 $250.51   8.597%   $272.0463   $272.05   $272.05   $272.00  
  Purchase #4 $111.84   7.454%   $120.1766   $120.18   $120.20   $120.20  
  Purchase #5 $204.96   10.482%   $226.4439   $226.44   $226.45   $226.40  
  Purchase #6 $126.75   4.306%   $132.2079   $132.21   $132.20   $132.20  
  Purchase #7 $61.65   11.103%   $68.495   $68.50   $68.50   $68.50  
  7 purchase totals = $1,020.27       $1,104.9440   $1,104.95   $1,105.00   $1,104.90