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	$189.85	11.768%	$212.1915	$212.19	$212.20	$212.20
Purchase #2	$61.60	10.200%	$67.8832	$67.88	$67.90	$67.90
Purchase #3	$64.41	4.810%	$67.5081	$67.51	$67.50	$67.50
Purchase #4	$31.65	10.342%	$34.9232	$34.92	$34.90	$34.90
Purchase #5	$79.31	9.533%	$86.8706	$86.87	$86.85	$86.90
Purchase #6	$243.78	4.265%	$254.1772	$254.18	$254.20	$254.20
Purchase #7	$241.94	3.630%	$250.7224	$250.72	$250.70	$250.70
7 purchase totals =	$912.54		$974.2762	$974.27	$974.25	$974.30