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	$44.31	4.271%	$46.2025	$46.20	$46.20	$46.20
Purchase #2	$40.61	8.133%	$43.9128	$43.91	$43.90	$43.90
Purchase #3	$114.29	8.372%	$123.8584	$123.86	$123.85	$123.90
Purchase #4	$90.69	10.838%	$100.519	$100.52	$100.50	$100.50
Purchase #5	$156.49	11.657%	$174.732	$174.73	$174.75	$174.70
Purchase #6	$52.55	12.515%	$59.1266	$59.13	$59.15	$59.10
Purchase #7	$31.29	10.189%	$34.4781	$34.48	$34.50	$34.50
7 purchase totals =	$530.23		$582.8294	$582.83	$582.85	$582.80