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	$58.30	4.553%	$60.9544	$60.95	$60.95	$61.00
Purchase #2	$33.27	5.692%	$35.1637	$35.16	$35.15	$35.20
Purchase #3	$13.98	5.707%	$14.7778	$14.78	$14.80	$14.80
Purchase #4	$64.40	4.505%	$67.3012	$67.30	$67.30	$67.30
Purchase #5	$110.94	11.470%	$123.6648	$123.66	$123.65	$123.70
Purchase #6	$74.47	12.221%	$83.571	$83.57	$83.55	$83.60
Purchase #7	$130.79	10.543%	$144.5792	$144.58	$144.60	$144.60
7 purchase totals =	$486.15		$530.0121	$530.00	$530.00	$530.20