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	$132.97	8.230%	$143.9134	$143.91	$143.90	$143.90
Purchase #2	$159.84	7.815%	$172.3315	$172.33	$172.35	$172.30
Purchase #3	$246.76	6.824%	$263.5989	$263.60	$263.60	$263.60
Purchase #4	$48.83	8.154%	$52.8116	$52.81	$52.80	$52.80
Purchase #5	$240.39	5.857%	$254.4696	$254.47	$254.45	$254.50
Purchase #6	$135.52	11.320%	$150.8609	$150.86	$150.85	$150.90
Purchase #7	$92.42	3.229%	$95.4042	$95.40	$95.40	$95.40
7 purchase totals =	$1,056.73		$1,133.3901	$1,133.38	$1,133.35	$1,133.40