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	$211.74	6.643%	$225.8059	$225.81	$225.80	$225.80
Purchase #2	$142.54	7.407%	$153.0979	$153.10	$153.10	$153.10
Purchase #3	$137.65	10.690%	$152.3648	$152.36	$152.35	$152.40
Purchase #4	$98.38	13.713%	$111.8708	$111.87	$111.85	$111.90
Purchase #5	$100.85	4.712%	$105.6021	$105.60	$105.60	$105.60
Purchase #6	$249.84	11.575%	$278.759	$278.76	$278.75	$278.80
Purchase #7	$233.25	9.488%	$255.3808	$255.38	$255.40	$255.40
7 purchase totals =	$1,174.25		$1,282.8813	$1,282.88	$1,282.85	$1,283.00