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	$136.25	6.607%	$145.252	$145.25	$145.25	$145.30
Purchase #2	$135.36	7.322%	$145.2711	$145.27	$145.25	$145.30
Purchase #3	$196.62	10.464%	$217.1943	$217.19	$217.20	$217.20
Purchase #4	$224.76	8.464%	$243.7837	$243.78	$243.80	$243.80
Purchase #5	$143.33	5.810%	$151.6575	$151.66	$151.65	$151.70
Purchase #6	$14.58	5.828%	$15.4297	$15.43	$15.45	$15.40
Purchase #7	$171.47	4.275%	$178.8003	$178.80	$178.80	$178.80
7 purchase totals =	$1,022.37		$1,097.3886	$1,097.38	$1,097.40	$1,097.50