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	$222.82	5.365%	$234.7743	$234.77	$234.75	$234.80
Purchase #2	$168.51	4.713%	$176.4519	$176.45	$176.45	$176.50
Purchase #3	$196.81	13.732%	$223.8359	$223.84	$223.85	$223.80
Purchase #4	$183.86	5.593%	$194.1433	$194.14	$194.15	$194.10
Purchase #5	$41.32	4.696%	$43.2604	$43.26	$43.25	$43.30
Purchase #6	$19.49	12.135%	$21.8551	$21.86	$21.85	$21.90
Purchase #7	$130.33	11.588%	$145.4326	$145.43	$145.45	$145.40
7 purchase totals =	$963.14		$1,039.7535	$1,039.75	$1,039.75	$1,039.80