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	$229.98	4.468%	$240.2555	$240.26	$240.25	$240.30
Purchase #2	$237.31	7.671%	$255.5141	$255.51	$255.50	$255.50
Purchase #3	$22.88	12.841%	$25.818	$25.82	$25.80	$25.80
Purchase #4	$211.83	5.262%	$222.9765	$222.98	$223.00	$223.00
Purchase #5	$69.53	8.629%	$75.5297	$75.53	$75.55	$75.50
Purchase #6	$31.45	4.494%	$32.8634	$32.86	$32.85	$32.90
Purchase #7	$248.94	7.105%	$266.6272	$266.63	$266.65	$266.60
7 purchase totals =	$1,051.92		$1,119.5844	$1,119.59	$1,119.60	$1,119.60