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	$250.40	6.417%	$266.4682	$266.47	$266.45	$266.50
Purchase #2	$155.81	4.423%	$162.7015	$162.70	$162.70	$162.70
Purchase #3	$30.61	8.276%	$33.1433	$33.14	$33.15	$33.10
Purchase #4	$223.45	4.503%	$233.512	$233.51	$233.50	$233.50
Purchase #5	$98.38	13.268%	$111.4331	$111.43	$111.45	$111.40
Purchase #6	$66.60	12.360%	$74.8318	$74.83	$74.85	$74.80
Purchase #7	$118.32	7.629%	$127.3466	$127.35	$127.35	$127.30
7 purchase totals =	$943.57		$1,009.4365	$1,009.43	$1,009.45	$1,009.30