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 $141.26   7.428%   $151.7528   $151.75   $151.75   $151.80  
  Purchase #2 $159.26   11.584%   $177.7087   $177.71   $177.70   $177.70  
  Purchase #3 $222.94   4.579%   $233.1484   $233.15   $233.15   $233.10  
  Purchase #4 $139.84   8.352%   $151.5194   $151.52   $151.50   $151.50  
  Purchase #5 $92.27   6.210%   $98   $98.00   $98.00   $98.00  
  Purchase #6 $40.78   7.873%   $43.9906   $43.99   $44.00   $44.00  
  Purchase #7 $209.26   5.315%   $220.3822   $220.38   $220.40   $220.40  
  7 purchase totals = $1,005.61       $1,076.5021   $1,076.50   $1,076.50   $1,076.50