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 $67.97   7.736%   $73.2282   $73.23   $73.25   $73.20  
  Purchase #2 $195.25   10.397%   $215.5501   $215.55   $215.55   $215.60  
  Purchase #3 $151.49   9.854%   $166.4178   $166.42   $166.40   $166.40  
  Purchase #4 $243.94   5.404%   $257.1225   $257.12   $257.10   $257.10  
  Purchase #5 $165.46   5.546%   $174.6364   $174.64   $174.65   $174.60  
  Purchase #6 $146.61   3.170%   $151.2575   $151.26   $151.25   $151.30  
  Purchase #7 $210.50   4.600%   $220.183   $220.18   $220.20   $220.20  
  7 purchase totals = $1,181.22       $1,258.3955   $1,258.40   $1,258.40   $1,258.40