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 $68.26   8.579%   $74.116   $74.12   $74.10   $74.10  
  Purchase #2 $93.39   4.268%   $97.3759   $97.38   $97.40   $97.40  
  Purchase #3 $170.34   7.109%   $182.4495   $182.45   $182.45   $182.40  
  Purchase #4 $60.88   12.692%   $68.6069   $68.61   $68.60   $68.60  
  Purchase #5 $213.80   4.117%   $222.6021   $222.60   $222.60   $222.60  
  Purchase #6 $202.33   9.279%   $221.1042   $221.10   $221.10   $221.10  
  Purchase #7 $90.39   12.460%   $101.6526   $101.65   $101.65   $101.70  
  7 purchase totals = $899.39       $967.9072   $967.91   $967.90   $967.90