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	$161.30	11.153%	$179.2898	$179.29	$179.30	$179.30
Purchase #2	$70.63	8.309%	$76.4986	$76.50	$76.50	$76.50
Purchase #3	$49.53	7.217%	$53.1046	$53.10	$53.10	$53.10
Purchase #4	$98.25	13.169%	$111.1885	$111.19	$111.20	$111.20
Purchase #5	$213.45	13.437%	$242.1313	$242.13	$242.15	$242.10
Purchase #6	$128.42	12.174%	$144.0539	$144.05	$144.05	$144.10
Purchase #7	$162.98	8.531%	$176.8838	$176.88	$176.90	$176.90
7 purchase totals =	$884.56		$983.1505	$983.14	$983.20	$983.20