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	$195.72	9.624%	$214.5561	$214.56	$214.55	$214.60
Purchase #2	$96.38	13.264%	$109.1638	$109.16	$109.15	$109.20
Purchase #3	$241.62	12.401%	$271.5833	$271.58	$271.60	$271.60
Purchase #4	$235.63	11.579%	$262.9136	$262.91	$262.90	$262.90
Purchase #5	$216.94	7.423%	$233.0435	$233.04	$233.05	$233.00
Purchase #6	$72.83	7.563%	$78.3381	$78.34	$78.35	$78.30
Purchase #7	$193.99	13.317%	$219.8236	$219.82	$219.80	$219.80
7 purchase totals =	$1,253.11		$1,389.4220	$1,389.41	$1,389.40	$1,389.40