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 $192.47   7.290%   $206.5011   $206.50   $206.50   $206.50  
  Purchase #2 $111.97   12.677%   $126.1644   $126.16   $126.15   $126.20  
  Purchase #3 $99.99   4.400%   $104.3896   $104.39   $104.40   $104.40  
  Purchase #4 $41.37   12.649%   $46.6029   $46.60   $46.60   $46.60  
  Purchase #5 $212.81   11.600%   $237.496   $237.50   $237.50   $237.50  
  Purchase #6 $188.96   12.858%   $213.2565   $213.26   $213.25   $213.30  
  Purchase #7 $149.54   7.265%   $160.4041   $160.40   $160.40   $160.40  
  7 purchase totals = $997.11       $1,094.8146   $1,094.81   $1,094.80   $1,094.90