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	$12.33	12.866%	$13.9164	$13.92	$13.90	$13.90
Purchase #2	$102.33	7.306%	$109.8062	$109.81	$109.80	$109.80
Purchase #3	$170.38	12.137%	$191.059	$191.06	$191.05	$191.10
Purchase #4	$113.68	4.587%	$118.8945	$118.89	$118.90	$118.90
Purchase #5	$61.81	4.324%	$64.4827	$64.48	$64.50	$64.50
Purchase #6	$112.74	12.252%	$126.5529	$126.55	$126.55	$126.60
Purchase #7	$111.85	13.579%	$127.0381	$127.04	$127.05	$127.00
7 purchase totals =	$685.12		$751.7498	$751.75	$751.75	$751.80