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	$110.30	7.689%	$118.781	$118.78	$118.80	$118.80
Purchase #2	$60.83	8.592%	$66.0565	$66.06	$66.05	$66.10
Purchase #3	$248.28	13.352%	$281.4303	$281.43	$281.45	$281.40
Purchase #4	$79.93	12.673%	$90.0595	$90.06	$90.05	$90.10
Purchase #5	$86.80	6.468%	$92.4142	$92.41	$92.40	$92.40
Purchase #6	$102.37	3.332%	$105.781	$105.78	$105.80	$105.80
Purchase #7	$245.76	7.857%	$265.0694	$265.07	$265.05	$265.10
7 purchase totals =	$934.27		$1,019.5919	$1,019.59	$1,019.60	$1,019.70