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 $195.84   5.367%   $206.3507   $206.35   $206.35   $206.40  
  Purchase #2 $63.29   3.674%   $65.6153   $65.62   $65.60   $65.60  
  Purchase #3 $113.88   4.648%   $119.1731   $119.17   $119.15   $119.20  
  Purchase #4 $140.29   11.825%   $156.8793   $156.88   $156.90   $156.90  
  Purchase #5 $99.74   6.488%   $106.2111   $106.21   $106.20   $106.20  
  Purchase #6 $51.27   3.433%   $53.0301   $53.03   $53.05   $53.00  
  Purchase #7 $90.86   5.261%   $95.6401   $95.64   $95.65   $95.60  
  7 purchase totals = $755.17       $802.8997   $802.90   $802.90   $802.90