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	$64.77	9.358%	$70.8312	$70.83	$70.85	$70.80
Purchase #2	$64.63	13.728%	$73.5024	$73.50	$73.50	$73.50
Purchase #3	$62.76	12.601%	$70.6684	$70.67	$70.65	$70.70
Purchase #4	$46.74	10.103%	$51.4621	$51.46	$51.45	$51.50
Purchase #5	$82.93	8.239%	$89.7626	$89.76	$89.75	$89.80
Purchase #6	$38.85	13.439%	$44.0711	$44.07	$44.05	$44.10
Purchase #7	$53.30	11.177%	$59.2573	$59.26	$59.25	$59.30
7 purchase totals =	$413.98		$459.5551	$459.55	$459.50	$459.70