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 $86.29   11.655%   $96.3471   $96.35   $96.35   $96.30  
  Purchase #2 $149.66   4.633%   $156.5937   $156.59   $156.60   $156.60  
  Purchase #3 $241.97   10.743%   $267.9648   $267.96   $267.95   $268.00  
  Purchase #4 $117.33   4.517%   $122.6298   $122.63   $122.65   $122.60  
  Purchase #5 $206.33   9.212%   $225.3371   $225.34   $225.35   $225.30  
  Purchase #6 $118.69   4.586%   $124.1331   $124.13   $124.15   $124.10  
  Purchase #7 $207.32   12.816%   $233.8901   $233.89   $233.90   $233.90  
  7 purchase totals = $1,127.59       $1,226.8957   $1,226.89   $1,226.95   $1,226.80