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	$50.63	12.291%	$56.8529	$56.85	$56.85	$56.90
Purchase #2	$52.27	8.751%	$56.8441	$56.84	$56.85	$56.80
Purchase #3	$100.92	12.109%	$113.1404	$113.14	$113.15	$113.10
Purchase #4	$90.37	5.597%	$95.428	$95.43	$95.45	$95.40
Purchase #5	$95.95	13.659%	$109.0558	$109.06	$109.05	$109.10
Purchase #6	$130.33	11.454%	$145.258	$145.26	$145.25	$145.30
Purchase #7	$46.78	6.560%	$49.8488	$49.85	$49.85	$49.80
7 purchase totals =	$567.25		$626.4280	$626.43	$626.45	$626.40