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	$243.86	8.169%	$263.7809	$263.78	$263.80	$263.80
Purchase #2	$83.61	10.552%	$92.4325	$92.43	$92.45	$92.40
Purchase #3	$159.62	4.745%	$167.194	$167.19	$167.20	$167.20
Purchase #4	$216.71	6.383%	$230.5426	$230.54	$230.55	$230.50
Purchase #5	$97.88	13.723%	$111.3121	$111.31	$111.30	$111.30
Purchase #6	$151.85	12.772%	$171.2443	$171.24	$171.25	$171.20
Purchase #7	$88.48	3.527%	$91.6007	$91.60	$91.60	$91.60
7 purchase totals =	$1,042.01		$1,128.1071	$1,128.09	$1,128.15	$1,128.00