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 $118.35   5.699%   $125.0948   $125.09   $125.10   $125.10  
  Purchase #2 $144.93   10.754%   $160.5158   $160.52   $160.50   $160.50  
  Purchase #3 $88.29   3.232%   $91.1435   $91.14   $91.15   $91.10  
  Purchase #4 $212.68   9.178%   $232.1998   $232.20   $232.20   $232.20  
  Purchase #5 $211.47   10.641%   $233.9725   $233.97   $233.95   $234.00  
  Purchase #6 $246.50   4.687%   $258.0535   $258.05   $258.05   $258.10  
  Purchase #7 $155.32   7.691%   $167.2657   $167.27   $167.25   $167.30  
  7 purchase totals = $1,177.54       $1,268.2456   $1,268.24   $1,268.20   $1,268.30