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 $60.57   3.616%   $62.7602   $62.76   $62.75   $62.80  
  Purchase #2 $110.74   11.738%   $123.7387   $123.74   $123.75   $123.70  
  Purchase #3 $164.98   8.165%   $178.4506   $178.45   $178.45   $178.50  
  Purchase #4 $138.49   8.373%   $150.0858   $150.09   $150.10   $150.10  
  Purchase #5 $179.73   10.567%   $198.7221   $198.72   $198.70   $198.70  
  Purchase #6 $188.36   9.417%   $206.0979   $206.10   $206.10   $206.10  
  Purchase #7 $245.78   10.784%   $272.2849   $272.28   $272.30   $272.30  
  7 purchase totals = $1,088.65       $1,192.1402   $1,192.14   $1,192.15   $1,192.20