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	$191.55	4.333%	$199.8499	$199.85	$199.85	$199.80
Purchase #2	$124.67	5.785%	$131.8822	$131.88	$131.90	$131.90
Purchase #3	$105.68	9.273%	$115.4797	$115.48	$115.50	$115.50
Purchase #4	$185.68	7.249%	$199.1399	$199.14	$199.15	$199.10
Purchase #5	$89.55	13.527%	$101.6634	$101.66	$101.65	$101.70
Purchase #6	$141.82	7.866%	$152.9756	$152.98	$153.00	$153.00
Purchase #7	$154.32	12.364%	$173.4001	$173.40	$173.40	$173.40
7 purchase totals =	$993.27		$1,074.3908	$1,074.39	$1,074.45	$1,074.40