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	$127.58	11.604%	$142.3844	$142.38	$142.40	$142.40
Purchase #2	$195.91	11.832%	$219.0901	$219.09	$219.10	$219.10
Purchase #3	$10.35	4.804%	$10.8472	$10.85	$10.85	$10.80
Purchase #4	$165.62	9.777%	$181.8127	$181.81	$181.80	$181.80
Purchase #5	$141.66	11.739%	$158.2895	$158.29	$158.30	$158.30
Purchase #6	$111.95	11.310%	$124.6115	$124.61	$124.60	$124.60
Purchase #7	$107.56	4.479%	$112.3776	$112.38	$112.40	$112.40
7 purchase totals =	$860.63		$949.4130	$949.41	$949.45	$949.40