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 $216.97   5.664%   $229.2592   $229.26   $229.25   $229.30  
  Purchase #2 $161.78   9.266%   $176.7705   $176.77   $176.75   $176.80  
  Purchase #3 $184.57   11.421%   $205.6497   $205.65   $205.65   $205.60  
  Purchase #4 $86.99   7.760%   $93.7404   $93.74   $93.75   $93.70  
  Purchase #5 $90.95   9.115%   $99.2401   $99.24   $99.25   $99.20  
  Purchase #6 $161.80   4.145%   $168.5066   $168.51   $168.50   $168.50  
  Purchase #7 $45.75   7.498%   $49.1803   $49.18   $49.20   $49.20  
  7 purchase totals = $948.81       $1,022.3468   $1,022.35   $1,022.35   $1,022.30