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	$161.91	11.851%	$181.098	$181.10	$181.10	$181.10
Purchase #2	$178.87	3.663%	$185.422	$185.42	$185.40	$185.40
Purchase #3	$113.59	3.631%	$117.7145	$117.71	$117.70	$117.70
Purchase #4	$140.77	8.302%	$152.4567	$152.46	$152.45	$152.50
Purchase #5	$219.87	11.115%	$244.3086	$244.31	$244.30	$244.30
Purchase #6	$68.95	5.420%	$72.6871	$72.69	$72.70	$72.70
Purchase #7	$35.64	13.314%	$40.3851	$40.39	$40.40	$40.40
7 purchase totals =	$919.60		$994.0720	$994.08	$994.05	$994.10