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	$208.49	10.184%	$229.7226	$229.72	$229.70	$229.70
Purchase #2	$233.87	5.536%	$246.817	$246.82	$246.80	$246.80
Purchase #3	$138.62	5.249%	$145.8962	$145.90	$145.90	$145.90
Purchase #4	$63.56	13.830%	$72.3503	$72.35	$72.35	$72.40
Purchase #5	$34.80	6.661%	$37.118	$37.12	$37.10	$37.10
Purchase #6	$58.31	10.167%	$64.2384	$64.24	$64.25	$64.20
Purchase #7	$172.39	7.724%	$185.7054	$185.71	$185.70	$185.70
7 purchase totals =	$910.04		$981.8479	$981.86	$981.80	$981.80