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	$217.52	7.535%	$233.9101	$233.91	$233.90	$233.90
Purchase #2	$105.80	10.785%	$117.2105	$117.21	$117.20	$117.20
Purchase #3	$13.59	13.477%	$15.4215	$15.42	$15.40	$15.40
Purchase #4	$97.65	8.335%	$105.7891	$105.79	$105.80	$105.80
Purchase #5	$232.52	3.700%	$241.1232	$241.12	$241.10	$241.10
Purchase #6	$243.63	10.841%	$270.0419	$270.04	$270.05	$270.00
Purchase #7	$160.83	12.788%	$181.3969	$181.40	$181.40	$181.40
7 purchase totals =	$1,071.54		$1,164.8932	$1,164.89	$1,164.85	$1,164.80