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	$51.73	3.471%	$53.5255	$53.53	$53.55	$53.50
Purchase #2	$22.28	10.307%	$24.5764	$24.58	$24.60	$24.60
Purchase #3	$37.87	5.324%	$39.8862	$39.89	$39.90	$39.90
Purchase #4	$34.58	9.539%	$37.8786	$37.88	$37.90	$37.90
Purchase #5	$51.46	7.303%	$55.2181	$55.22	$55.20	$55.20
Purchase #6	$79.26	10.336%	$87.4523	$87.45	$87.45	$87.50
Purchase #7	$57.64	6.837%	$61.5808	$61.58	$61.60	$61.60
7 purchase totals =	$334.82		$360.1179	$360.13	$360.20	$360.20