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	$219.35	11.491%	$244.5555	$244.56	$244.55	$244.60
Purchase #2	$92.25	3.483%	$95.4631	$95.46	$95.45	$95.50
Purchase #3	$136.62	12.669%	$153.9284	$153.93	$153.95	$153.90
Purchase #4	$149.90	12.334%	$168.3887	$168.39	$168.40	$168.40
Purchase #5	$158.69	9.551%	$173.8465	$173.85	$173.85	$173.80
Purchase #6	$136.70	11.814%	$152.8497	$152.85	$152.85	$152.80
Purchase #7	$215.74	12.384%	$242.4572	$242.46	$242.45	$242.50
7 purchase totals =	$1,109.25		$1,231.4891	$1,231.50	$1,231.50	$1,231.50