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 $66.25   10.241%   $73.0347   $73.03   $73.05   $73.00  
  Purchase #2 $26.78   7.169%   $28.6999   $28.70   $28.70   $28.70  
  Purchase #3 $191.40   4.297%   $199.6245   $199.62   $199.60   $199.60  
  Purchase #4 $216.80   9.810%   $238.0681   $238.07   $238.05   $238.10  
  Purchase #5 $217.94   12.399%   $244.9624   $244.96   $244.95   $245.00  
  Purchase #6 $240.60   9.279%   $262.9253   $262.93   $262.95   $262.90  
  Purchase #7 $113.86   5.697%   $120.3466   $120.35   $120.35   $120.30  
  7 purchase totals = $1,073.63       $1,167.6615   $1,167.66   $1,167.65   $1,167.60