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 $245.54   7.227%   $263.2852   $263.29   $263.30   $263.30  
  Purchase #2 $246.69   12.144%   $276.648   $276.65   $276.65   $276.60  
  Purchase #3 $171.53   5.260%   $180.5525   $180.55   $180.55   $180.60  
  Purchase #4 $126.58   5.110%   $133.0482   $133.05   $133.05   $133.00  
  Purchase #5 $216.39   6.834%   $231.1781   $231.18   $231.20   $231.20  
  Purchase #6 $173.69   11.387%   $193.4681   $193.47   $193.45   $193.50  
  Purchase #7 $192.45   12.784%   $217.0528   $217.05   $217.05   $217.10  
  7 purchase totals = $1,372.87       $1,495.2329   $1,495.24   $1,495.25   $1,495.30