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	$248.49	11.321%	$276.6216	$276.62	$276.60	$276.60
Purchase #2	$200.90	4.301%	$209.5407	$209.54	$209.55	$209.50
Purchase #3	$52.34	5.423%	$55.1784	$55.18	$55.20	$55.20
Purchase #4	$52.66	7.323%	$56.5163	$56.52	$56.50	$56.50
Purchase #5	$53.85	3.838%	$55.9168	$55.92	$55.90	$55.90
Purchase #6	$224.82	4.521%	$234.9841	$234.98	$235.00	$235.00
Purchase #7	$65.54	12.501%	$73.7332	$73.73	$73.75	$73.70
7 purchase totals =	$898.60		$962.4911	$962.49	$962.50	$962.40