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 $244.91   7.480%   $263.2293   $263.23   $263.25   $263.20  
  Purchase #2 $169.69   7.386%   $182.2233   $182.22   $182.20   $182.20  
  Purchase #3 $56.62   6.253%   $60.1604   $60.16   $60.15   $60.20  
  Purchase #4 $212.77   9.611%   $233.2193   $233.22   $233.20   $233.20  
  Purchase #5 $31.57   13.341%   $35.7818   $35.78   $35.80   $35.80  
  Purchase #6 $201.82   7.355%   $216.6639   $216.66   $216.65   $216.70  
  Purchase #7 $185.89   3.650%   $192.675   $192.68   $192.70   $192.70  
  7 purchase totals = $1,103.27       $1,183.9530   $1,183.95   $1,183.95   $1,184.00