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	$162.72	6.431%	$173.1845	$173.18	$173.20	$173.20
Purchase #2	$72.99	6.149%	$77.4782	$77.48	$77.50	$77.50
Purchase #3	$116.88	3.212%	$120.6342	$120.63	$120.65	$120.60
Purchase #4	$221.63	7.526%	$238.3099	$238.31	$238.30	$238.30
Purchase #5	$151.66	12.514%	$170.6387	$170.64	$170.65	$170.60
Purchase #6	$103.91	7.162%	$111.352	$111.35	$111.35	$111.40
Purchase #7	$188.32	11.150%	$209.3177	$209.32	$209.30	$209.30
7 purchase totals =	$1,018.11		$1,100.9152	$1,100.91	$1,100.95	$1,100.90