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	$53.58	11.606%	$59.7985	$59.80	$59.80	$59.80
Purchase #2	$138.69	9.563%	$151.9529	$151.95	$151.95	$152.00
Purchase #3	$235.41	13.517%	$267.2304	$267.23	$267.25	$267.20
Purchase #4	$182.56	6.761%	$194.9029	$194.90	$194.90	$194.90
Purchase #5	$151.58	4.840%	$158.9165	$158.92	$158.90	$158.90
Purchase #6	$35.56	11.349%	$39.5957	$39.60	$39.60	$39.60
Purchase #7	$155.71	13.693%	$177.0314	$177.03	$177.05	$177.00
7 purchase totals =	$953.09		$1,049.4283	$1,049.43	$1,049.45	$1,049.40