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	$241.87	7.471%	$259.9401	$259.94	$259.95	$259.90
Purchase #2	$156.61	10.751%	$173.4471	$173.45	$173.45	$173.40
Purchase #3	$19.60	5.538%	$20.6854	$20.69	$20.70	$20.70
Purchase #4	$204.93	13.168%	$231.9152	$231.92	$231.90	$231.90
Purchase #5	$60.33	10.820%	$66.8577	$66.86	$66.85	$66.90
Purchase #6	$16.51	11.481%	$18.4055	$18.41	$18.40	$18.40
Purchase #7	$66.63	6.577%	$71.0123	$71.01	$71.00	$71.00
7 purchase totals =	$766.48		$842.2633	$842.28	$842.25	$842.20