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 $118.65   5.326%   $124.9693   $124.97   $124.95   $125.00  
  Purchase #2 $95.28   13.203%   $107.8598   $107.86   $107.85   $107.90  
  Purchase #3 $135.89   4.642%   $142.198   $142.20   $142.20   $142.20  
  Purchase #4 $240.90   12.239%   $270.3838   $270.38   $270.40   $270.40  
  Purchase #5 $10.78   10.123%   $11.8713   $11.87   $11.85   $11.90  
  Purchase #6 $77.33   10.377%   $85.3545   $85.35   $85.35   $85.40  
  Purchase #7 $109.58   8.269%   $118.6412   $118.64   $118.65   $118.60  
  7 purchase totals = $788.41       $861.2779   $861.27   $861.25   $861.40