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	$186.97	5.228%	$196.7448	$196.74	$196.75	$196.70
Purchase #2	$112.65	9.843%	$123.7381	$123.74	$123.75	$123.70
Purchase #3	$163.54	13.249%	$185.2074	$185.21	$185.20	$185.20
Purchase #4	$192.69	12.430%	$216.6414	$216.64	$216.65	$216.60
Purchase #5	$44.94	13.265%	$50.9013	$50.90	$50.90	$50.90
Purchase #6	$52.57	7.491%	$56.508	$56.51	$56.50	$56.50
Purchase #7	$105.52	4.631%	$110.4066	$110.41	$110.40	$110.40
7 purchase totals =	$858.88		$940.1476	$940.15	$940.15	$940.00