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	$191.90	4.607%	$200.7408	$200.74	$200.75	$200.70
Purchase #2	$157.81	9.555%	$172.8887	$172.89	$172.90	$172.90
Purchase #3	$5.53	6.248%	$5.8755	$5.88	$5.90	$5.90
Purchase #4	$90.51	11.175%	$100.6245	$100.62	$100.60	$100.60
Purchase #5	$137.66	3.359%	$142.284	$142.28	$142.30	$142.30
Purchase #6	$209.37	5.255%	$220.3724	$220.37	$220.35	$220.40
Purchase #7	$58.77	11.594%	$65.5838	$65.58	$65.60	$65.60
7 purchase totals =	$851.55		$908.3697	$908.36	$908.40	$908.40