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	$230.29	7.104%	$246.6498	$246.65	$246.65	$246.60
Purchase #2	$97.72	10.308%	$107.793	$107.79	$107.80	$107.80
Purchase #3	$82.44	8.385%	$89.3526	$89.35	$89.35	$89.40
Purchase #4	$118.34	8.816%	$128.7729	$128.77	$128.75	$128.80
Purchase #5	$144.96	6.340%	$154.1505	$154.15	$154.15	$154.20
Purchase #6	$87.25	13.654%	$99.1631	$99.16	$99.15	$99.20
Purchase #7	$53.72	10.178%	$59.1876	$59.19	$59.20	$59.20
7 purchase totals =	$814.72		$885.0695	$885.06	$885.05	$885.20