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	$190.36	5.445%	$200.7251	$200.73	$200.75	$200.70
Purchase #2	$20.99	4.788%	$21.995	$22.00	$22.00	$22.00
Purchase #3	$240.73	10.694%	$266.4737	$266.47	$266.45	$266.50
Purchase #4	$229.35	5.759%	$242.5583	$242.56	$242.55	$242.60
Purchase #5	$199.61	11.674%	$222.9125	$222.91	$222.90	$222.90
Purchase #6	$153.47	13.146%	$173.6452	$173.65	$173.65	$173.60
Purchase #7	$63.46	13.347%	$71.93	$71.93	$71.95	$71.90
7 purchase totals =	$1,097.97		$1,200.2398	$1,200.25	$1,200.25	$1,200.20