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	$55.91	4.689%	$58.5316	$58.53	$58.55	$58.50
Purchase #2	$88.72	13.454%	$100.6564	$100.66	$100.65	$100.70
Purchase #3	$139.67	3.296%	$144.2735	$144.27	$144.25	$144.30
Purchase #4	$153.34	5.259%	$161.4042	$161.40	$161.40	$161.40
Purchase #5	$86.93	13.405%	$98.583	$98.58	$98.60	$98.60
Purchase #6	$40.45	13.580%	$45.9431	$45.94	$45.95	$45.90
Purchase #7	$139.84	12.463%	$157.2683	$157.27	$157.25	$157.30
7 purchase totals =	$704.86		$766.6601	$766.65	$766.65	$766.70