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	$66.85	7.178%	$71.6485	$71.65	$71.65	$71.60
Purchase #2	$100.31	13.406%	$113.7576	$113.76	$113.75	$113.80
Purchase #3	$250.43	5.617%	$264.4967	$264.50	$264.50	$264.50
Purchase #4	$22.54	9.223%	$24.6189	$24.62	$24.60	$24.60
Purchase #5	$190.52	3.240%	$196.6928	$196.69	$196.70	$196.70
Purchase #6	$216.63	10.591%	$239.5733	$239.57	$239.55	$239.60
Purchase #7	$193.28	4.574%	$202.1206	$202.12	$202.10	$202.10
7 purchase totals =	$1,040.56		$1,112.9084	$1,112.91	$1,112.85	$1,112.90