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	$45.39	11.575%	$50.6439	$50.64	$50.65	$50.60
Purchase #2	$151.31	6.334%	$160.894	$160.89	$160.90	$160.90
Purchase #3	$92.74	12.104%	$103.9652	$103.97	$103.95	$104.00
Purchase #4	$35.58	11.779%	$39.771	$39.77	$39.75	$39.80
Purchase #5	$41.42	10.437%	$45.743	$45.74	$45.75	$45.70
Purchase #6	$33.88	5.651%	$35.7946	$35.79	$35.80	$35.80
Purchase #7	$42.63	7.378%	$45.7752	$45.78	$45.80	$45.80
7 purchase totals =	$442.95		$482.5869	$482.58	$482.60	$482.60