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 $198.74   8.812%   $216.253   $216.25   $216.25   $216.30  
  Purchase #2 $83.36   10.311%   $91.9552   $91.96   $91.95   $92.00  
  Purchase #3 $176.69   9.781%   $193.972   $193.97   $193.95   $194.00  
  Purchase #4 $97.67   8.821%   $106.2855   $106.29   $106.30   $106.30  
  Purchase #5 $64.37   13.651%   $73.1571   $73.16   $73.15   $73.20  
  Purchase #6 $180.92   10.831%   $200.5154   $200.52   $200.50   $200.50  
  Purchase #7 $246.35   8.756%   $267.9204   $267.92   $267.90   $267.90  
  7 purchase totals = $1,048.10       $1,150.0586   $1,150.07   $1,150.00   $1,150.20