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 $218.42   5.760%   $231.001   $231.00   $231.00   $231.00  
  Purchase #2 $101.40   13.362%   $114.9491   $114.95   $114.95   $114.90  
  Purchase #3 $162.33   6.693%   $173.1947   $173.19   $173.20   $173.20  
  Purchase #4 $159.70   5.707%   $168.8141   $168.81   $168.80   $168.80  
  Purchase #5 $66.63   12.815%   $75.1686   $75.17   $75.15   $75.20  
  Purchase #6 $210.99   5.851%   $223.335   $223.34   $223.35   $223.30  
  Purchase #7 $93.36   6.249%   $99.1941   $99.19   $99.20   $99.20  
  7 purchase totals = $1,012.83       $1,085.6566   $1,085.65   $1,085.65   $1,085.60