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	$152.42	4.669%	$159.5365	$159.54	$159.55	$159.50
Purchase #2	$215.50	10.661%	$238.4745	$238.47	$238.45	$238.50
Purchase #3	$6.58	7.212%	$7.0545	$7.05	$7.05	$7.10
Purchase #4	$142.60	11.851%	$159.4995	$159.50	$159.50	$159.50
Purchase #5	$207.76	12.700%	$234.1455	$234.15	$234.15	$234.10
Purchase #6	$83.88	4.435%	$87.6001	$87.60	$87.60	$87.60
Purchase #7	$224.25	12.745%	$252.8307	$252.83	$252.85	$252.80
7 purchase totals =	$1,032.99		$1,139.1413	$1,139.14	$1,139.15	$1,139.10