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	$61.92	7.591%	$66.6203	$66.62	$66.60	$66.60
Purchase #2	$66.38	13.557%	$75.3791	$75.38	$75.40	$75.40
Purchase #3	$17.92	13.370%	$20.3159	$20.32	$20.30	$20.30
Purchase #4	$248.98	4.644%	$260.5426	$260.54	$260.55	$260.50
Purchase #5	$105.68	7.364%	$113.4623	$113.46	$113.45	$113.50
Purchase #6	$40.31	12.806%	$45.4721	$45.47	$45.45	$45.50
Purchase #7	$139.59	8.716%	$151.7567	$151.76	$151.75	$151.80
7 purchase totals =	$680.78		$733.5490	$733.55	$733.50	$733.60