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	$104.91	3.399%	$108.4759	$108.48	$108.50	$108.50
Purchase #2	$200.72	8.448%	$217.6768	$217.68	$217.70	$217.70
Purchase #3	$100.38	7.430%	$107.8382	$107.84	$107.85	$107.80
Purchase #4	$136.43	11.168%	$151.6665	$151.67	$151.65	$151.70
Purchase #5	$138.25	10.456%	$152.7054	$152.71	$152.70	$152.70
Purchase #6	$142.88	12.701%	$161.0272	$161.03	$161.05	$161.00
Purchase #7	$175.47	11.785%	$196.1491	$196.15	$196.15	$196.10
7 purchase totals =	$999.04		$1,095.5391	$1,095.56	$1,095.60	$1,095.50