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	$41.55	13.806%	$47.2864	$47.29	$47.30	$47.30
Purchase #2	$37.75	4.513%	$39.4537	$39.45	$39.45	$39.50
Purchase #3	$85.33	6.622%	$90.9806	$90.98	$91.00	$91.00
Purchase #4	$209.90	6.299%	$223.1216	$223.12	$223.10	$223.10
Purchase #5	$28.67	13.641%	$32.5809	$32.58	$32.60	$32.60
Purchase #6	$151.54	4.570%	$158.4654	$158.47	$158.45	$158.50
Purchase #7	$120.86	11.401%	$134.6392	$134.64	$134.65	$134.60
7 purchase totals =	$675.60		$726.5278	$726.53	$726.55	$726.60