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 $84.29   13.254%   $95.4618   $95.46   $95.45   $95.50  
  Purchase #2 $85.73   12.313%   $96.2859   $96.29   $96.30   $96.30  
  Purchase #3 $54.91   7.184%   $58.8547   $58.85   $58.85   $58.90  
  Purchase #4 $60.44   8.530%   $65.5955   $65.60   $65.60   $65.60  
  Purchase #5 $195.35   12.628%   $220.0188   $220.02   $220.00   $220.00  
  Purchase #6 $53.63   5.311%   $56.4783   $56.48   $56.50   $56.50  
  Purchase #7 $172.68   10.731%   $191.2103   $191.21   $191.20   $191.20  
  7 purchase totals = $707.03       $783.9053   $783.91   $783.90   $784.00