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	$154.38	13.551%	$175.3	$175.30	$175.30	$175.30
Purchase #2	$194.83	11.599%	$217.4283	$217.43	$217.45	$217.40
Purchase #3	$241.89	8.368%	$262.1314	$262.13	$262.15	$262.10
Purchase #4	$111.62	4.312%	$116.4331	$116.43	$116.45	$116.40
Purchase #5	$142.29	6.727%	$151.8618	$151.86	$151.85	$151.90
Purchase #6	$114.74	11.660%	$128.1187	$128.12	$128.10	$128.10
Purchase #7	$42.80	9.649%	$46.9298	$46.93	$46.95	$46.90
7 purchase totals =	$1,002.55		$1,098.2031	$1,098.20	$1,098.25	$1,098.10