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	$162.29	5.445%	$171.1267	$171.13	$171.15	$171.10
Purchase #2	$60.41	4.791%	$63.3042	$63.30	$63.30	$63.30
Purchase #3	$127.76	11.361%	$142.2748	$142.27	$142.25	$142.30
Purchase #4	$71.79	10.765%	$79.5182	$79.52	$79.50	$79.50
Purchase #5	$171.89	11.834%	$192.2315	$192.23	$192.25	$192.20
Purchase #6	$101.30	7.142%	$108.5348	$108.53	$108.55	$108.50
Purchase #7	$147.32	8.348%	$159.6183	$159.62	$159.60	$159.60
7 purchase totals =	$842.76		$916.6085	$916.60	$916.60	$916.50