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	$206.57	10.697%	$228.6668	$228.67	$228.65	$228.70
Purchase #2	$240.75	13.172%	$272.4616	$272.46	$272.45	$272.50
Purchase #3	$32.38	3.467%	$33.5026	$33.50	$33.50	$33.50
Purchase #4	$147.37	8.266%	$159.5516	$159.55	$159.55	$159.60
Purchase #5	$152.93	13.448%	$173.496	$173.50	$173.50	$173.50
Purchase #6	$141.35	9.770%	$155.1599	$155.16	$155.15	$155.20
Purchase #7	$148.59	9.170%	$162.2157	$162.22	$162.20	$162.20
7 purchase totals =	$1,069.94		$1,185.0542	$1,185.06	$1,185.00	$1,185.20