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	$110.83	11.422%	$123.489	$123.49	$123.50	$123.50
Purchase #2	$22.61	7.497%	$24.3051	$24.31	$24.30	$24.30
Purchase #3	$210.86	8.795%	$229.4051	$229.41	$229.40	$229.40
Purchase #4	$174.45	10.818%	$193.322	$193.32	$193.30	$193.30
Purchase #5	$106.46	11.353%	$118.5464	$118.55	$118.55	$118.50
Purchase #6	$40.79	12.693%	$45.9675	$45.97	$45.95	$46.00
Purchase #7	$151.50	13.864%	$172.504	$172.50	$172.50	$172.50
7 purchase totals =	$817.50		$907.5391	$907.55	$907.50	$907.50