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	$53.86	11.261%	$59.9252	$59.93	$59.95	$59.90
Purchase #2	$103.25	8.110%	$111.6236	$111.62	$111.60	$111.60
Purchase #3	$149.44	4.250%	$155.7912	$155.79	$155.80	$155.80
Purchase #4	$10.49	13.506%	$11.9068	$11.91	$11.90	$11.90
Purchase #5	$74.91	5.129%	$78.7521	$78.75	$78.75	$78.80
Purchase #6	$202.25	8.613%	$219.6698	$219.67	$219.65	$219.70
Purchase #7	$128.38	4.872%	$134.6347	$134.63	$134.65	$134.60
7 purchase totals =	$722.58		$772.3034	$772.30	$772.30	$772.30