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	$196.34	7.626%	$211.3129	$211.31	$211.30	$211.30
Purchase #2	$158.61	7.626%	$170.7056	$170.71	$170.70	$170.70
Purchase #3	$49.33	4.386%	$51.4936	$51.49	$51.50	$51.50
Purchase #4	$134.49	7.365%	$144.3952	$144.40	$144.40	$144.40
Purchase #5	$173.43	9.161%	$189.3179	$189.32	$189.30	$189.30
Purchase #6	$157.39	9.836%	$172.8709	$172.87	$172.85	$172.90
Purchase #7	$57.48	5.319%	$60.5374	$60.54	$60.55	$60.50
7 purchase totals =	$927.07		$1,000.6335	$1,000.64	$1,000.60	$1,000.60