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	$96.39	13.657%	$109.554	$109.55	$109.55	$109.60
Purchase #2	$216.71	7.624%	$233.232	$233.23	$233.25	$233.20
Purchase #3	$194.27	13.191%	$219.8962	$219.90	$219.90	$219.90
Purchase #4	$140.61	3.235%	$145.1587	$145.16	$145.15	$145.20
Purchase #5	$68.90	3.769%	$71.4968	$71.50	$71.50	$71.50
Purchase #6	$47.55	9.828%	$52.2232	$52.22	$52.20	$52.20
Purchase #7	$247.79	3.503%	$256.4701	$256.47	$256.45	$256.50
7 purchase totals =	$1,012.22		$1,088.0310	$1,088.03	$1,088.00	$1,088.10