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 $62.93   6.397%   $66.9556   $66.96   $66.95   $67.00  
  Purchase #2 $65.71   8.717%   $71.4379   $71.44   $71.45   $71.40  
  Purchase #3 $147.90   4.286%   $154.239   $154.24   $154.25   $154.20  
  Purchase #4 $80.86   3.634%   $83.7985   $83.80   $83.80   $83.80  
  Purchase #5 $98.97   7.692%   $106.5828   $106.58   $106.60   $106.60  
  Purchase #6 $7.93   5.858%   $8.3945   $8.39   $8.40   $8.40  
  Purchase #7 $206.65   13.401%   $234.3432   $234.34   $234.35   $234.30  
  7 purchase totals = $670.95       $725.7515   $725.75   $725.80   $725.70