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 $105.56   12.786%   $119.0569   $119.06   $119.05   $119.10  
  Purchase #2 $147.35   5.325%   $155.1964   $155.20   $155.20   $155.20  
  Purchase #3 $66.27   5.769%   $70.0931   $70.09   $70.10   $70.10  
  Purchase #4 $195.86   9.185%   $213.8497   $213.85   $213.85   $213.80  
  Purchase #5 $84.44   10.163%   $93.0216   $93.02   $93.00   $93.00  
  Purchase #6 $247.27   9.650%   $271.1316   $271.13   $271.15   $271.10  
  Purchase #7 $104.48   4.599%   $109.285   $109.29   $109.30   $109.30  
  7 purchase totals = $951.23       $1,031.6343   $1,031.64   $1,031.65   $1,031.60