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	$158.86	3.409%	$164.2755	$164.28	$164.30	$164.30
Purchase #2	$165.52	5.383%	$174.4299	$174.43	$174.45	$174.40
Purchase #3	$122.31	4.524%	$127.8433	$127.84	$127.85	$127.80
Purchase #4	$50.25	12.743%	$56.6534	$56.65	$56.65	$56.70
Purchase #5	$110.56	12.467%	$124.3435	$124.34	$124.35	$124.30
Purchase #6	$234.53	3.376%	$242.4477	$242.45	$242.45	$242.40
Purchase #7	$113.59	3.517%	$117.585	$117.59	$117.60	$117.60
7 purchase totals =	$955.62		$1,007.5783	$1,007.58	$1,007.65	$1,007.50