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	$141.59	4.389%	$147.8044	$147.80	$147.80	$147.80
Purchase #2	$235.71	10.113%	$259.5474	$259.55	$259.55	$259.50
Purchase #3	$6.97	3.750%	$7.2314	$7.23	$7.25	$7.20
Purchase #4	$244.34	3.612%	$253.1656	$253.17	$253.15	$253.20
Purchase #5	$168.33	3.123%	$173.5869	$173.59	$173.60	$173.60
Purchase #6	$170.65	12.436%	$191.872	$191.87	$191.85	$191.90
Purchase #7	$220.37	4.181%	$229.5837	$229.58	$229.60	$229.60
7 purchase totals =	$1,187.96		$1,262.7914	$1,262.79	$1,262.80	$1,262.80