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	$76.72	11.818%	$85.7868	$85.79	$85.80	$85.80
Purchase #2	$157.67	13.640%	$179.1762	$179.18	$179.20	$179.20
Purchase #3	$14.86	11.185%	$16.5221	$16.52	$16.50	$16.50
Purchase #4	$59.34	3.782%	$61.5842	$61.58	$61.60	$61.60
Purchase #5	$134.73	8.303%	$145.9166	$145.92	$145.90	$145.90
Purchase #6	$30.50	7.556%	$32.8046	$32.80	$32.80	$32.80
Purchase #7	$34.63	11.725%	$38.6904	$38.69	$38.70	$38.70
7 purchase totals =	$508.45		$560.4809	$560.48	$560.50	$560.50