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	$190.87	10.435%	$210.7873	$210.79	$210.80	$210.80
Purchase #2	$92.73	10.403%	$102.3767	$102.38	$102.40	$102.40
Purchase #3	$224.91	13.762%	$255.8621	$255.86	$255.85	$255.90
Purchase #4	$137.63	6.570%	$146.6723	$146.67	$146.65	$146.70
Purchase #5	$43.51	12.314%	$48.8678	$48.87	$48.85	$48.90
Purchase #6	$189.45	8.426%	$205.4131	$205.41	$205.40	$205.40
Purchase #7	$108.38	5.667%	$114.5219	$114.52	$114.50	$114.50
7 purchase totals =	$987.48		$1,084.5012	$1,084.50	$1,084.45	$1,084.60