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	$208.25	7.868%	$224.6351	$224.64	$224.65	$224.60
Purchase #2	$205.83	12.335%	$231.2191	$231.22	$231.20	$231.20
Purchase #3	$148.34	13.363%	$168.1627	$168.16	$168.15	$168.20
Purchase #4	$168.76	10.367%	$186.2553	$186.26	$186.25	$186.30
Purchase #5	$70.40	3.431%	$72.8154	$72.82	$72.80	$72.80
Purchase #6	$171.90	12.278%	$193.0059	$193.01	$193.00	$193.00
Purchase #7	$88.43	13.787%	$100.6218	$100.62	$100.60	$100.60
7 purchase totals =	$1,061.91		$1,176.7153	$1,176.73	$1,176.65	$1,176.70