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	$114.70	11.165%	$127.5063	$127.51	$127.50	$127.50
Purchase #2	$32.92	13.772%	$37.4537	$37.45	$37.45	$37.50
Purchase #3	$122.25	13.601%	$138.8772	$138.88	$138.90	$138.90
Purchase #4	$59.83	10.807%	$66.2958	$66.30	$66.30	$66.30
Purchase #5	$116.60	13.237%	$132.0343	$132.03	$132.05	$132.00
Purchase #6	$32.68	10.506%	$36.1134	$36.11	$36.10	$36.10
Purchase #7	$76.69	7.142%	$82.1672	$82.17	$82.15	$82.20
7 purchase totals =	$555.67		$620.4479	$620.45	$620.45	$620.50