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	$166.46	7.579%	$179.076	$179.08	$179.10	$179.10
Purchase #2	$24.92	9.355%	$27.2513	$27.25	$27.25	$27.30
Purchase #3	$162.79	13.492%	$184.7536	$184.75	$184.75	$184.80
Purchase #4	$65.43	11.288%	$72.8157	$72.82	$72.80	$72.80
Purchase #5	$179.29	13.123%	$202.8182	$202.82	$202.80	$202.80
Purchase #6	$139.61	10.539%	$154.3235	$154.32	$154.30	$154.30
Purchase #7	$9.89	10.182%	$10.897	$10.90	$10.90	$10.90
7 purchase totals =	$748.39		$831.9353	$831.94	$831.90	$832.00