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 $42.55   3.441%   $44.0141   $44.01   $44.00   $44.00  
  Purchase #2 $133.39   13.729%   $151.7031   $151.70   $151.70   $151.70  
  Purchase #3 $200.66   8.454%   $217.6238   $217.62   $217.60   $217.60  
  Purchase #4 $182.42   5.187%   $191.8821   $191.88   $191.90   $191.90  
  Purchase #5 $139.54   11.536%   $155.6373   $155.64   $155.65   $155.60  
  Purchase #6 $152.96   9.195%   $167.0247   $167.02   $167.00   $167.00  
  Purchase #7 $244.47   11.772%   $273.249   $273.25   $273.25   $273.20  
  7 purchase totals = $1,095.99       $1,201.1341   $1,201.12   $1,201.10   $1,201.00