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	$33.45	11.334%	$37.2412	$37.24	$37.25	$37.20
Purchase #2	$27.97	3.713%	$29.0085	$29.01	$29.00	$29.00
Purchase #3	$184.28	11.462%	$205.4022	$205.40	$205.40	$205.40
Purchase #4	$149.72	5.862%	$158.4966	$158.50	$158.50	$158.50
Purchase #5	$82.61	11.758%	$92.3233	$92.32	$92.30	$92.30
Purchase #6	$165.60	11.700%	$184.9752	$184.98	$185.00	$185.00
Purchase #7	$87.44	8.217%	$94.6249	$94.62	$94.60	$94.60
7 purchase totals =	$731.07		$802.0719	$802.07	$802.05	$802.00