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	$223.82	3.378%	$231.3806	$231.38	$231.40	$231.40
Purchase #2	$136.40	4.463%	$142.4875	$142.49	$142.50	$142.50
Purchase #3	$118.46	11.667%	$132.2807	$132.28	$132.30	$132.30
Purchase #4	$25.88	11.635%	$28.8911	$28.89	$28.90	$28.90
Purchase #5	$25.68	8.739%	$27.9242	$27.92	$27.90	$27.90
Purchase #6	$171.29	13.261%	$194.0048	$194.00	$194.00	$194.00
Purchase #7	$39.45	11.431%	$43.9595	$43.96	$43.95	$44.00
7 purchase totals =	$740.98		$800.9284	$800.92	$800.95	$801.00