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	$187.69	9.368%	$205.2728	$205.27	$205.25	$205.30
Purchase #2	$179.89	6.337%	$191.2896	$191.29	$191.30	$191.30
Purchase #3	$39.66	13.670%	$45.0815	$45.08	$45.10	$45.10
Purchase #4	$84.60	7.603%	$91.0321	$91.03	$91.05	$91.00
Purchase #5	$197.29	13.842%	$224.5989	$224.60	$224.60	$224.60
Purchase #6	$105.88	4.401%	$110.5398	$110.54	$110.55	$110.50
Purchase #7	$130.59	10.501%	$144.3033	$144.30	$144.30	$144.30
7 purchase totals =	$925.60		$1,012.1180	$1,012.11	$1,012.15	$1,012.10