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	$146.71	6.676%	$156.5044	$156.50	$156.50	$156.50
Purchase #2	$166.85	3.747%	$173.1019	$173.10	$173.10	$173.10
Purchase #3	$113.76	7.519%	$122.3136	$122.31	$122.30	$122.30
Purchase #4	$120.82	11.578%	$134.8085	$134.81	$134.80	$134.80
Purchase #5	$155.41	9.132%	$169.602	$169.60	$169.60	$169.60
Purchase #6	$106.40	4.552%	$111.2433	$111.24	$111.25	$111.20
Purchase #7	$138.50	7.429%	$148.7892	$148.79	$148.80	$148.80
7 purchase totals =	$948.45		$1,016.3629	$1,016.35	$1,016.35	$1,016.30