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	$208.35	13.490%	$236.4564	$236.46	$236.45	$236.50
Purchase #2	$79.94	3.623%	$82.8362	$82.84	$82.85	$82.80
Purchase #3	$221.28	13.538%	$251.2369	$251.24	$251.25	$251.20
Purchase #4	$92.84	6.697%	$99.0575	$99.06	$99.05	$99.10
Purchase #5	$6.43	13.239%	$7.2813	$7.28	$7.30	$7.30
Purchase #6	$235.74	12.725%	$265.7379	$265.74	$265.75	$265.70
Purchase #7	$124.58	13.865%	$141.853	$141.85	$141.85	$141.90
7 purchase totals =	$969.16		$1,084.4592	$1,084.47	$1,084.50	$1,084.50