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 $176.93   10.127%   $194.8477   $194.85   $194.85   $194.80  
  Purchase #2 $41.42   9.241%   $45.2476   $45.25   $45.25   $45.20  
  Purchase #3 $99.26   11.324%   $110.5002   $110.50   $110.50   $110.50  
  Purchase #4 $178.51   7.212%   $191.3841   $191.38   $191.40   $191.40  
  Purchase #5 $186.68   9.464%   $204.3474   $204.35   $204.35   $204.30  
  Purchase #6 $155.29   11.627%   $173.3456   $173.35   $173.35   $173.30  
  Purchase #7 $234.65   8.808%   $255.318   $255.32   $255.30   $255.30  
  7 purchase totals = $1,072.74       $1,174.9906   $1,175.00   $1,175.00   $1,174.80