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	$49.54	5.369%	$52.1998	$52.20	$52.20	$52.20
Purchase #2	$160.56	13.346%	$181.9883	$181.99	$182.00	$182.00
Purchase #3	$125.59	10.627%	$138.9364	$138.94	$138.95	$138.90
Purchase #4	$163.65	10.534%	$180.8889	$180.89	$180.90	$180.90
Purchase #5	$155.70	11.111%	$172.9998	$173.00	$173.00	$173.00
Purchase #6	$86.57	3.672%	$89.7489	$89.75	$89.75	$89.70
Purchase #7	$145.39	4.200%	$151.4964	$151.50	$151.50	$151.50
7 purchase totals =	$887.00		$968.2585	$968.27	$968.30	$968.20