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	$101.76	3.463%	$105.2839	$105.28	$105.30	$105.30
Purchase #2	$210.66	6.574%	$224.5088	$224.51	$224.50	$224.50
Purchase #3	$240.50	6.206%	$255.4254	$255.43	$255.45	$255.40
Purchase #4	$60.57	3.131%	$62.4664	$62.47	$62.45	$62.50
Purchase #5	$242.45	3.325%	$250.5115	$250.51	$250.50	$250.50
Purchase #6	$47.54	8.698%	$51.675	$51.68	$51.70	$51.70
Purchase #7	$231.92	10.309%	$255.8286	$255.83	$255.85	$255.80
7 purchase totals =	$1,135.40		$1,205.6996	$1,205.71	$1,205.75	$1,205.70