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	$34.64	5.707%	$36.6169	$36.62	$36.60	$36.60
Purchase #2	$150.38	5.795%	$159.0945	$159.09	$159.10	$159.10
Purchase #3	$106.48	4.539%	$111.3131	$111.31	$111.30	$111.30
Purchase #4	$105.73	3.408%	$109.3333	$109.33	$109.35	$109.30
Purchase #5	$66.92	3.862%	$69.5045	$69.50	$69.50	$69.50
Purchase #6	$59.59	7.609%	$64.1242	$64.12	$64.10	$64.10
Purchase #7	$38.52	6.531%	$41.0357	$41.04	$41.05	$41.00
7 purchase totals =	$562.26		$591.0222	$591.01	$591.00	$590.90