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 $246.65   7.562%   $265.3017   $265.30   $265.30   $265.30  
  Purchase #2 $209.77   9.321%   $229.3227   $229.32   $229.30   $229.30  
  Purchase #3 $159.61   7.642%   $171.8074   $171.81   $171.80   $171.80  
  Purchase #4 $150.60   12.355%   $169.2066   $169.21   $169.20   $169.20  
  Purchase #5 $159.56   8.844%   $173.6715   $173.67   $173.65   $173.70  
  Purchase #6 $231.53   3.746%   $240.2031   $240.20   $240.20   $240.20  
  Purchase #7 $231.88   6.304%   $246.4977   $246.50   $246.50   $246.50  
  7 purchase totals = $1,389.60       $1,496.0107   $1,496.01   $1,495.95   $1,496.00