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	$152.36	13.781%	$173.3567	$173.36	$173.35	$173.40
Purchase #2	$205.70	5.496%	$217.0053	$217.01	$217.00	$217.00
Purchase #3	$155.53	7.723%	$167.5416	$167.54	$167.55	$167.50
Purchase #4	$25.55	11.333%	$28.4456	$28.45	$28.45	$28.40
Purchase #5	$51.47	8.513%	$55.8516	$55.85	$55.85	$55.90
Purchase #6	$159.31	4.173%	$165.958	$165.96	$165.95	$166.00
Purchase #7	$225.72	8.152%	$244.1207	$244.12	$244.10	$244.10
7 purchase totals =	$975.64		$1,052.2795	$1,052.29	$1,052.25	$1,052.30