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	$204.78	4.627%	$214.2552	$214.26	$214.25	$214.30
Purchase #2	$56.52	10.674%	$62.5529	$62.55	$62.55	$62.60
Purchase #3	$41.73	8.206%	$45.1544	$45.15	$45.15	$45.20
Purchase #4	$245.47	6.573%	$261.6047	$261.60	$261.60	$261.60
Purchase #5	$65.71	10.508%	$72.6148	$72.61	$72.60	$72.60
Purchase #6	$237.94	10.311%	$262.474	$262.47	$262.45	$262.50
Purchase #7	$75.25	13.458%	$85.3771	$85.38	$85.40	$85.40
7 purchase totals =	$927.40		$1,004.0331	$1,004.02	$1,004.00	$1,004.20