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	$168.41	8.476%	$182.6844	$182.68	$182.70	$182.70
Purchase #2	$80.81	12.757%	$91.1189	$91.12	$91.10	$91.10
Purchase #3	$54.45	8.436%	$59.0434	$59.04	$59.05	$59.00
Purchase #4	$128.75	13.707%	$146.3978	$146.40	$146.40	$146.40
Purchase #5	$50.78	4.271%	$52.9488	$52.95	$52.95	$52.90
Purchase #6	$242.79	5.820%	$256.9204	$256.92	$256.90	$256.90
Purchase #7	$151.27	13.171%	$171.1938	$171.19	$171.20	$171.20
7 purchase totals =	$877.26		$960.3075	$960.30	$960.30	$960.20