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	$61.95	10.433%	$68.4132	$68.41	$68.40	$68.40
Purchase #2	$83.64	12.535%	$94.1243	$94.12	$94.10	$94.10
Purchase #3	$140.61	7.464%	$151.1051	$151.11	$151.10	$151.10
Purchase #4	$5.55	6.422%	$5.9064	$5.91	$5.90	$5.90
Purchase #5	$45.28	3.631%	$46.9241	$46.92	$46.90	$46.90
Purchase #6	$101.78	7.224%	$109.1326	$109.13	$109.15	$109.10
Purchase #7	$114.48	11.474%	$127.6154	$127.62	$127.60	$127.60
7 purchase totals =	$553.29		$603.2211	$603.22	$603.15	$603.10