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 $93.66   10.292%   $103.2995   $103.30   $103.30   $103.30  
  Purchase #2 $215.44   12.306%   $241.952   $241.95   $241.95   $242.00  
  Purchase #3 $220.96   12.419%   $248.401   $248.40   $248.40   $248.40  
  Purchase #4 $199.45   10.497%   $220.3863   $220.39   $220.40   $220.40  
  Purchase #5 $187.88   9.694%   $206.0931   $206.09   $206.10   $206.10  
  Purchase #6 $105.82   11.293%   $117.7703   $117.77   $117.75   $117.80  
  Purchase #7 $22.96   7.831%   $24.758   $24.76   $24.75   $24.80  
  7 purchase totals = $1,046.17       $1,162.6602   $1,162.66   $1,162.65   $1,162.80