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	$166.83	3.436%	$172.5623	$172.56	$172.55	$172.60
Purchase #2	$18.76	3.164%	$19.3536	$19.35	$19.35	$19.40
Purchase #3	$235.73	12.590%	$265.4084	$265.41	$265.40	$265.40
Purchase #4	$213.80	11.500%	$238.387	$238.39	$238.40	$238.40
Purchase #5	$150.45	10.192%	$165.7839	$165.78	$165.80	$165.80
Purchase #6	$118.93	9.475%	$130.1986	$130.20	$130.20	$130.20
Purchase #7	$12.27	6.830%	$13.108	$13.11	$13.10	$13.10
7 purchase totals =	$916.77		$1,004.8018	$1,004.80	$1,004.80	$1,004.90