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	$81.32	7.681%	$87.5662	$87.57	$87.55	$87.60
Purchase #2	$146.85	4.153%	$152.9487	$152.95	$152.95	$152.90
Purchase #3	$15.52	4.560%	$16.2277	$16.23	$16.25	$16.20
Purchase #4	$79.80	8.837%	$86.8519	$86.85	$86.85	$86.90
Purchase #5	$74.47	5.431%	$78.5145	$78.51	$78.50	$78.50
Purchase #6	$21.83	3.490%	$22.5919	$22.59	$22.60	$22.60
Purchase #7	$170.69	5.406%	$179.9175	$179.92	$179.90	$179.90
7 purchase totals =	$590.48		$624.6184	$624.62	$624.60	$624.60