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	$132.48	12.166%	$148.5975	$148.60	$148.60	$148.60
Purchase #2	$77.42	12.166%	$86.8389	$86.84	$86.85	$86.80
Purchase #3	$97.94	5.520%	$103.3463	$103.35	$103.35	$103.30
Purchase #4	$148.75	4.648%	$155.6639	$155.66	$155.65	$155.70
Purchase #5	$153.37	9.834%	$168.4524	$168.45	$168.45	$168.50
Purchase #6	$157.54	10.201%	$173.6107	$173.61	$173.60	$173.60
Purchase #7	$219.81	4.216%	$229.0772	$229.08	$229.10	$229.10
7 purchase totals =	$987.31		$1,065.5869	$1,065.59	$1,065.60	$1,065.60