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 $58.95   13.770%   $67.0674   $67.07   $67.05   $67.10  
  Purchase #2 $161.42   9.618%   $176.9454   $176.95   $176.95   $176.90  
  Purchase #3 $152.76   10.837%   $169.3146   $169.31   $169.30   $169.30  
  Purchase #4 $6.71   9.736%   $7.3633   $7.36   $7.35   $7.40  
  Purchase #5 $153.30   6.572%   $163.3749   $163.37   $163.35   $163.40  
  Purchase #6 $155.38   13.287%   $176.0253   $176.03   $176.05   $176.00  
  Purchase #7 $156.51   12.792%   $176.5308   $176.53   $176.55   $176.50  
  7 purchase totals = $845.03       $936.6217   $936.62   $936.60   $936.60