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	$142.86	13.233%	$161.7647	$161.76	$161.75	$161.80
Purchase #2	$26.98	8.118%	$29.1702	$29.17	$29.15	$29.20
Purchase #3	$151.95	4.296%	$158.4778	$158.48	$158.50	$158.50
Purchase #4	$83.36	12.278%	$93.5949	$93.59	$93.60	$93.60
Purchase #5	$115.96	12.113%	$130.0062	$130.01	$130.00	$130.00
Purchase #6	$39.52	9.652%	$43.3345	$43.33	$43.35	$43.30
Purchase #7	$105.65	5.865%	$111.8464	$111.85	$111.85	$111.80
7 purchase totals =	$666.28		$728.1947	$728.19	$728.20	$728.20