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	$243.32	8.739%	$264.5837	$264.58	$264.60	$264.60
Purchase #2	$177.46	4.285%	$185.0642	$185.06	$185.05	$185.10
Purchase #3	$139.81	4.557%	$146.1811	$146.18	$146.20	$146.20
Purchase #4	$35.90	4.570%	$37.5406	$37.54	$37.55	$37.50
Purchase #5	$230.62	8.151%	$249.4178	$249.42	$249.40	$249.40
Purchase #6	$235.72	10.284%	$259.9614	$259.96	$259.95	$260.00
Purchase #7	$145.37	4.387%	$151.7474	$151.75	$151.75	$151.70
7 purchase totals =	$1,208.20		$1,294.4962	$1,294.49	$1,294.50	$1,294.50