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	$35.34	5.608%	$37.3219	$37.32	$37.30	$37.30
Purchase #2	$225.92	12.569%	$254.3159	$254.32	$254.30	$254.30
Purchase #3	$146.60	3.791%	$152.1576	$152.16	$152.15	$152.20
Purchase #4	$132.60	6.363%	$141.0373	$141.04	$141.05	$141.00
Purchase #5	$88.57	12.864%	$99.9636	$99.96	$99.95	$100.00
Purchase #6	$216.35	4.461%	$226.0014	$226.00	$226.00	$226.00
Purchase #7	$45.52	6.351%	$48.411	$48.41	$48.40	$48.40
7 purchase totals =	$890.90		$959.2087	$959.21	$959.15	$959.20