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	$153.38	6.672%	$163.6135	$163.61	$163.60	$163.60
Purchase #2	$221.74	10.432%	$244.8719	$244.87	$244.85	$244.90
Purchase #3	$232.62	6.451%	$247.6263	$247.63	$247.65	$247.60
Purchase #4	$172.40	4.182%	$179.6098	$179.61	$179.60	$179.60
Purchase #5	$179.64	11.797%	$200.8321	$200.83	$200.85	$200.80
Purchase #6	$31.64	11.831%	$35.3833	$35.38	$35.40	$35.40
Purchase #7	$113.55	12.185%	$127.3861	$127.39	$127.40	$127.40
7 purchase totals =	$1,104.97		$1,199.3230	$1,199.32	$1,199.35	$1,199.30