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	$40.91	11.454%	$45.5958	$45.60	$45.60	$45.60
Purchase #2	$231.48	7.252%	$248.2669	$248.27	$248.25	$248.30
Purchase #3	$235.87	13.718%	$268.2266	$268.23	$268.25	$268.20
Purchase #4	$96.39	3.685%	$99.942	$99.94	$99.95	$99.90
Purchase #5	$106.61	4.754%	$111.6782	$111.68	$111.70	$111.70
Purchase #6	$83.34	3.534%	$86.2852	$86.29	$86.30	$86.30
Purchase #7	$139.78	13.205%	$158.2379	$158.24	$158.25	$158.20
7 purchase totals =	$934.38		$1,018.2326	$1,018.25	$1,018.30	$1,018.20