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	$53.76	5.845%	$56.9023	$56.90	$56.90	$56.90
Purchase #2	$173.74	13.701%	$197.5441	$197.54	$197.55	$197.50
Purchase #3	$238.28	13.433%	$270.2882	$270.29	$270.30	$270.30
Purchase #4	$103.30	8.317%	$111.8915	$111.89	$111.90	$111.90
Purchase #5	$96.75	8.683%	$105.1508	$105.15	$105.15	$105.20
Purchase #6	$14.41	3.812%	$14.9593	$14.96	$14.95	$15.00
Purchase #7	$250.80	11.502%	$279.647	$279.65	$279.65	$279.60
7 purchase totals =	$931.04		$1,036.3832	$1,036.38	$1,036.40	$1,036.40