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 $60.64   4.270%   $63.2293   $63.23   $63.25   $63.20  
  Purchase #2 $108.42   4.394%   $113.184   $113.18   $113.20   $113.20  
  Purchase #3 $118.57   6.618%   $126.417   $126.42   $126.40   $126.40  
  Purchase #4 $247.74   5.246%   $260.7364   $260.74   $260.75   $260.70  
  Purchase #5 $85.73   5.507%   $90.4512   $90.45   $90.45   $90.50  
  Purchase #6 $5.63   7.252%   $6.0383   $6.04   $6.05   $6.00  
  Purchase #7 $130.88   3.755%   $135.7945   $135.79   $135.80   $135.80  
  7 purchase totals = $757.61       $795.8507   $795.85   $795.90   $795.80