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	$247.90	13.768%	$282.0309	$282.03	$282.05	$282.00
Purchase #2	$165.41	4.534%	$172.9097	$172.91	$172.90	$172.90
Purchase #3	$60.78	7.796%	$65.5184	$65.52	$65.50	$65.50
Purchase #4	$59.31	10.532%	$65.5565	$65.56	$65.55	$65.60
Purchase #5	$208.72	12.415%	$234.6326	$234.63	$234.65	$234.60
Purchase #6	$92.40	12.299%	$103.7643	$103.76	$103.75	$103.80
Purchase #7	$72.68	6.503%	$77.4064	$77.41	$77.40	$77.40
7 purchase totals =	$907.20		$1,001.8188	$1,001.82	$1,001.80	$1,001.80