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	$20.51	5.625%	$21.6637	$21.66	$21.65	$21.70
Purchase #2	$186.72	3.726%	$193.6772	$193.68	$193.70	$193.70
Purchase #3	$215.89	10.619%	$238.8154	$238.82	$238.80	$238.80
Purchase #4	$57.71	4.446%	$60.2758	$60.28	$60.30	$60.30
Purchase #5	$108.94	4.194%	$113.5089	$113.51	$113.50	$113.50
Purchase #6	$179.33	5.439%	$189.0838	$189.08	$189.10	$189.10
Purchase #7	$236.40	3.445%	$244.544	$244.54	$244.55	$244.50
7 purchase totals =	$1,005.50		$1,061.5688	$1,061.57	$1,061.60	$1,061.60