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	$144.33	6.428%	$153.6075	$153.61	$153.60	$153.60
Purchase #2	$118.75	5.165%	$124.8834	$124.88	$124.90	$124.90
Purchase #3	$241.66	5.284%	$254.4293	$254.43	$254.45	$254.40
Purchase #4	$17.32	4.205%	$18.0483	$18.05	$18.05	$18.00
Purchase #5	$200.28	4.560%	$209.4128	$209.41	$209.40	$209.40
Purchase #6	$73.98	5.179%	$77.8114	$77.81	$77.80	$77.80
Purchase #7	$230.28	10.784%	$255.1134	$255.11	$255.10	$255.10
7 purchase totals =	$1,026.60		$1,093.3061	$1,093.30	$1,093.30	$1,093.20