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	$98.46	13.306%	$111.5611	$111.56	$111.55	$111.60
Purchase #2	$176.80	7.314%	$189.7312	$189.73	$189.75	$189.70
Purchase #3	$153.51	8.742%	$166.9298	$166.93	$166.95	$166.90
Purchase #4	$145.91	13.243%	$165.2329	$165.23	$165.25	$165.20
Purchase #5	$142.75	7.175%	$152.9923	$152.99	$153.00	$153.00
Purchase #6	$120.88	5.121%	$127.0703	$127.07	$127.05	$127.10
Purchase #7	$219.77	11.369%	$244.7557	$244.76	$244.75	$244.80
7 purchase totals =	$1,058.08		$1,158.2733	$1,158.27	$1,158.30	$1,158.30