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 $182.44   7.213%   $195.5994   $195.60   $195.60   $195.60  
  Purchase #2 $150.85   12.400%   $169.5554   $169.56   $169.55   $169.60  
  Purchase #3 $223.99   10.461%   $247.4216   $247.42   $247.40   $247.40  
  Purchase #4 $150.55   11.256%   $167.4959   $167.50   $167.50   $167.50  
  Purchase #5 $167.62   9.605%   $183.7199   $183.72   $183.70   $183.70  
  Purchase #6 $110.96   5.506%   $117.0695   $117.07   $117.05   $117.10  
  Purchase #7 $238.76   11.319%   $265.7852   $265.79   $265.80   $265.80  
  7 purchase totals = $1,225.17       $1,346.6469   $1,346.66   $1,346.60   $1,346.70