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	$173.50	7.769%	$186.9792	$186.98	$187.00	$187.00
Purchase #2	$39.54	10.152%	$43.5541	$43.55	$43.55	$43.60
Purchase #3	$76.30	8.411%	$82.7176	$82.72	$82.70	$82.70
Purchase #4	$175.90	4.173%	$183.2403	$183.24	$183.25	$183.20
Purchase #5	$99.25	4.651%	$103.8661	$103.87	$103.85	$103.90
Purchase #6	$162.58	6.134%	$172.5527	$172.55	$172.55	$172.60
Purchase #7	$95.68	8.298%	$103.6195	$103.62	$103.60	$103.60
7 purchase totals =	$822.75		$876.5295	$876.53	$876.50	$876.60