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	$204.66	4.548%	$213.9679	$213.97	$213.95	$214.00
Purchase #2	$196.74	13.377%	$223.0579	$223.06	$223.05	$223.10
Purchase #3	$164.58	8.378%	$178.3685	$178.37	$178.35	$178.40
Purchase #4	$58.94	13.348%	$66.8073	$66.81	$66.80	$66.80
Purchase #5	$246.90	5.642%	$260.8301	$260.83	$260.85	$260.80
Purchase #6	$73.75	12.162%	$82.7195	$82.72	$82.70	$82.70
Purchase #7	$48.54	9.446%	$53.1251	$53.13	$53.15	$53.10
7 purchase totals =	$994.11		$1,078.8763	$1,078.89	$1,078.85	$1,078.90