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	$188.69	6.481%	$200.919	$200.92	$200.90	$200.90
Purchase #2	$120.93	13.767%	$137.5784	$137.58	$137.60	$137.60
Purchase #3	$168.38	10.823%	$186.6038	$186.60	$186.60	$186.60
Purchase #4	$154.93	12.151%	$173.7555	$173.76	$173.75	$173.80
Purchase #5	$154.59	11.666%	$172.6245	$172.62	$172.60	$172.60
Purchase #6	$94.93	4.283%	$98.9959	$99.00	$99.00	$99.00
Purchase #7	$37.34	13.793%	$42.4903	$42.49	$42.50	$42.50
7 purchase totals =	$919.79		$1,012.9674	$1,012.97	$1,012.95	$1,013.00