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 $74.53   3.127%   $76.8606   $76.86   $76.85   $76.90  
  Purchase #2 $200.61   5.174%   $210.9896   $210.99   $211.00   $211.00  
  Purchase #3 $230.75   10.404%   $254.7572   $254.76   $254.75   $254.80  
  Purchase #4 $62.33   9.421%   $68.2021   $68.20   $68.20   $68.20  
  Purchase #5 $46.46   13.576%   $52.7674   $52.77   $52.75   $52.80  
  Purchase #6 $80.77   9.856%   $88.7307   $88.73   $88.75   $88.70  
  Purchase #7 $248.52   9.322%   $271.687   $271.69   $271.70   $271.70  
  7 purchase totals = $943.97       $1,023.9946   $1,024.00   $1,024.00   $1,024.10