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	$224.82	3.119%	$231.8321	$231.83	$231.85	$231.80
Purchase #2	$227.76	4.748%	$238.574	$238.57	$238.55	$238.60
Purchase #3	$75.69	12.399%	$85.0748	$85.07	$85.05	$85.10
Purchase #4	$101.82	9.578%	$111.5723	$111.57	$111.55	$111.60
Purchase #5	$243.92	11.303%	$271.4903	$271.49	$271.50	$271.50
Purchase #6	$214.92	9.681%	$235.7264	$235.73	$235.75	$235.70
Purchase #7	$146.80	13.135%	$166.0822	$166.08	$166.10	$166.10
7 purchase totals =	$1,235.73		$1,340.3521	$1,340.34	$1,340.35	$1,340.40