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	$206.70	11.553%	$230.5801	$230.58	$230.60	$230.60
Purchase #2	$151.73	13.325%	$171.948	$171.95	$171.95	$171.90
Purchase #3	$243.89	10.571%	$269.6716	$269.67	$269.65	$269.70
Purchase #4	$18.83	12.638%	$21.2097	$21.21	$21.20	$21.20
Purchase #5	$65.27	11.447%	$72.7415	$72.74	$72.75	$72.70
Purchase #6	$146.77	3.845%	$152.4133	$152.41	$152.40	$152.40
Purchase #7	$142.26	3.397%	$147.0926	$147.09	$147.10	$147.10
7 purchase totals =	$975.45		$1,065.6568	$1,065.65	$1,065.65	$1,065.60