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	$9.83	9.311%	$10.7453	$10.75	$10.75	$10.70
Purchase #2	$95.61	5.144%	$100.5282	$100.53	$100.55	$100.50
Purchase #3	$216.49	8.563%	$235.028	$235.03	$235.05	$235.00
Purchase #4	$72.75	13.104%	$82.2832	$82.28	$82.30	$82.30
Purchase #5	$44.65	11.138%	$49.6231	$49.62	$49.60	$49.60
Purchase #6	$234.98	8.871%	$255.8251	$255.83	$255.85	$255.80
Purchase #7	$22.47	10.417%	$24.8107	$24.81	$24.80	$24.80
7 purchase totals =	$696.78		$758.8436	$758.85	$758.90	$758.70