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	$60.37	10.578%	$66.7559	$66.76	$66.75	$66.80
Purchase #2	$153.30	7.651%	$165.029	$165.03	$165.05	$165.00
Purchase #3	$85.56	7.677%	$92.1284	$92.13	$92.15	$92.10
Purchase #4	$168.60	13.146%	$190.7642	$190.76	$190.75	$190.80
Purchase #5	$104.75	4.861%	$109.8419	$109.84	$109.85	$109.80
Purchase #6	$161.92	3.599%	$167.7475	$167.75	$167.75	$167.70
Purchase #7	$169.89	9.707%	$186.3812	$186.38	$186.40	$186.40
7 purchase totals =	$904.39		$978.6481	$978.65	$978.70	$978.60