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 $92.54   4.658%   $96.8505   $96.85   $96.85   $96.90  
  Purchase #2 $181.94   8.487%   $197.3812   $197.38   $197.40   $197.40  
  Purchase #3 $16.70   13.415%   $18.9403   $18.94   $18.95   $18.90  
  Purchase #4 $90.86   9.246%   $99.2609   $99.26   $99.25   $99.30  
  Purchase #5 $181.42   6.138%   $192.5556   $192.56   $192.55   $192.60  
  Purchase #6 $115.77   7.744%   $124.7352   $124.74   $124.75   $124.70  
  Purchase #7 $14.43   13.662%   $16.4014   $16.40   $16.40   $16.40  
  7 purchase totals = $693.66       $746.1251   $746.13   $746.15   $746.20