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	$159.37	6.366%	$169.5155	$169.52	$169.50	$169.50
Purchase #2	$29.65	9.280%	$32.4015	$32.40	$32.40	$32.40
Purchase #3	$176.49	11.106%	$196.091	$196.09	$196.10	$196.10
Purchase #4	$166.75	8.831%	$181.4757	$181.48	$181.50	$181.50
Purchase #5	$13.74	12.766%	$15.494	$15.49	$15.50	$15.50
Purchase #6	$162.78	6.369%	$173.1475	$173.15	$173.15	$173.10
Purchase #7	$229.25	9.856%	$251.8449	$251.84	$251.85	$251.80
7 purchase totals =	$938.03		$1,019.9701	$1,019.97	$1,020.00	$1,019.90