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	$144.50	3.829%	$150.0329	$150.03	$150.05	$150.00
Purchase #2	$25.27	11.445%	$28.1622	$28.16	$28.15	$28.20
Purchase #3	$125.50	9.815%	$137.8178	$137.82	$137.80	$137.80
Purchase #4	$162.90	6.351%	$173.2458	$173.25	$173.25	$173.20
Purchase #5	$225.88	12.813%	$254.822	$254.82	$254.80	$254.80
Purchase #6	$73.35	5.491%	$77.3776	$77.38	$77.40	$77.40
Purchase #7	$74.33	3.700%	$77.0802	$77.08	$77.10	$77.10
7 purchase totals =	$831.73		$898.5385	$898.54	$898.55	$898.50