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	$21.68	11.806%	$24.2395	$24.24	$24.25	$24.20
Purchase #2	$36.92	7.133%	$39.5535	$39.55	$39.55	$39.60
Purchase #3	$54.51	5.748%	$57.6432	$57.64	$57.65	$57.60
Purchase #4	$67.41	7.511%	$72.4732	$72.47	$72.45	$72.50
Purchase #5	$87.46	10.442%	$96.5926	$96.59	$96.60	$96.60
Purchase #6	$173.81	3.431%	$179.7734	$179.77	$179.75	$179.80
Purchase #7	$238.64	7.655%	$256.9079	$256.91	$256.90	$256.90
7 purchase totals =	$680.43		$727.1833	$727.17	$727.15	$727.20