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	$183.81	9.412%	$201.1102	$201.11	$201.10	$201.10
Purchase #2	$94.61	6.408%	$100.6726	$100.67	$100.65	$100.70
Purchase #3	$25.42	8.255%	$27.5184	$27.52	$27.50	$27.50
Purchase #4	$108.71	7.776%	$117.1633	$117.16	$117.15	$117.20
Purchase #5	$145.41	11.834%	$162.6178	$162.62	$162.60	$162.60
Purchase #6	$10.47	13.496%	$11.883	$11.88	$11.90	$11.90
Purchase #7	$162.42	3.604%	$168.2736	$168.27	$168.25	$168.30
7 purchase totals =	$730.85		$789.2389	$789.23	$789.15	$789.30