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 $61.74   13.301%   $69.952   $69.95   $69.95   $70.00  
  Purchase #2 $112.51   12.753%   $126.8584   $126.86   $126.85   $126.90  
  Purchase #3 $207.34   7.302%   $222.48   $222.48   $222.50   $222.50  
  Purchase #4 $205.61   11.773%   $229.8165   $229.82   $229.80   $229.80  
  Purchase #5 $28.46   3.224%   $29.3776   $29.38   $29.40   $29.40  
  Purchase #6 $220.80   6.366%   $234.8561   $234.86   $234.85   $234.90  
  Purchase #7 $50.50   5.110%   $53.0806   $53.08   $53.10   $53.10  
  7 purchase totals = $886.96       $966.4212   $966.43   $966.45   $966.60