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	$218.61	9.225%	$238.7768	$238.78	$238.80	$238.80
Purchase #2	$144.39	11.130%	$160.4606	$160.46	$160.45	$160.50
Purchase #3	$140.40	5.793%	$148.5334	$148.53	$148.55	$148.50
Purchase #4	$174.40	6.784%	$186.2313	$186.23	$186.25	$186.20
Purchase #5	$153.25	12.674%	$172.6729	$172.67	$172.65	$172.70
Purchase #6	$167.77	10.822%	$185.9261	$185.93	$185.95	$185.90
Purchase #7	$54.74	10.332%	$60.3957	$60.40	$60.40	$60.40
7 purchase totals =	$1,053.56		$1,152.9968	$1,153.00	$1,153.05	$1,153.00