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	$127.61	8.253%	$138.1417	$138.14	$138.15	$138.10
Purchase #2	$162.38	7.290%	$174.2175	$174.22	$174.20	$174.20
Purchase #3	$11.87	13.429%	$13.464	$13.46	$13.45	$13.50
Purchase #4	$247.98	10.732%	$274.5932	$274.59	$274.60	$274.60
Purchase #5	$119.42	7.366%	$128.2165	$128.22	$128.20	$128.20
Purchase #6	$149.69	8.397%	$162.2595	$162.26	$162.25	$162.30
Purchase #7	$118.45	7.438%	$127.2603	$127.26	$127.25	$127.30
7 purchase totals =	$937.40		$1,018.1527	$1,018.15	$1,018.10	$1,018.20