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	$106.71	4.362%	$111.3647	$111.36	$111.35	$111.40
Purchase #2	$96.26	5.584%	$101.6352	$101.64	$101.65	$101.60
Purchase #3	$227.60	11.445%	$253.6488	$253.65	$253.65	$253.60
Purchase #4	$114.83	7.750%	$123.7293	$123.73	$123.75	$123.70
Purchase #5	$45.29	5.763%	$47.9001	$47.90	$47.90	$47.90
Purchase #6	$78.34	13.483%	$88.9026	$88.90	$88.90	$88.90
Purchase #7	$153.83	9.433%	$168.3408	$168.34	$168.35	$168.30
7 purchase totals =	$822.86		$895.5215	$895.52	$895.55	$895.40