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	$157.30	8.863%	$171.2415	$171.24	$171.25	$171.20
Purchase #2	$145.61	10.685%	$161.1684	$161.17	$161.15	$161.20
Purchase #3	$154.62	11.181%	$171.9081	$171.91	$171.90	$171.90
Purchase #4	$142.87	7.393%	$153.4324	$153.43	$153.45	$153.40
Purchase #5	$40.35	12.763%	$45.4999	$45.50	$45.50	$45.50
Purchase #6	$190.74	11.432%	$212.5454	$212.55	$212.55	$212.50
Purchase #7	$158.29	6.366%	$168.3667	$168.37	$168.35	$168.40
7 purchase totals =	$989.78		$1,084.1624	$1,084.17	$1,084.15	$1,084.10