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	$172.73	10.230%	$190.4003	$190.40	$190.40	$190.40
Purchase #2	$15.29	13.440%	$17.345	$17.35	$17.35	$17.30
Purchase #3	$60.83	8.771%	$66.1654	$66.17	$66.15	$66.20
Purchase #4	$37.43	3.258%	$38.6495	$38.65	$38.65	$38.60
Purchase #5	$212.74	3.797%	$220.8177	$220.82	$220.80	$220.80
Purchase #6	$14.40	10.280%	$15.8803	$15.88	$15.90	$15.90
Purchase #7	$158.89	8.353%	$172.1621	$172.16	$172.15	$172.20
7 purchase totals =	$672.31		$721.4203	$721.43	$721.40	$721.40