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 $83.90   12.751%   $94.5981   $94.60   $94.60   $94.60  
  Purchase #2 $63.84   6.466%   $67.9679   $67.97   $67.95   $68.00  
  Purchase #3 $86.29   8.163%   $93.3339   $93.33   $93.35   $93.30  
  Purchase #4 $9.84   4.443%   $10.2772   $10.28   $10.30   $10.30  
  Purchase #5 $39.33   9.776%   $43.1749   $43.17   $43.15   $43.20  
  Purchase #6 $237.65   3.406%   $245.7444   $245.74   $245.75   $245.70  
  Purchase #7 $169.91   5.387%   $179.0631   $179.06   $179.05   $179.10  
  7 purchase totals = $690.76       $734.1595   $734.15   $734.15   $734.20