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	$45.56	6.773%	$48.6458	$48.65	$48.65	$48.60
Purchase #2	$231.61	12.381%	$260.2856	$260.29	$260.30	$260.30
Purchase #3	$192.72	4.261%	$200.9318	$200.93	$200.95	$200.90
Purchase #4	$46.28	6.577%	$49.3238	$49.32	$49.30	$49.30
Purchase #5	$207.51	9.802%	$227.8501	$227.85	$227.85	$227.90
Purchase #6	$91.98	7.202%	$98.6044	$98.60	$98.60	$98.60
Purchase #7	$89.72	13.115%	$101.4868	$101.49	$101.50	$101.50
7 purchase totals =	$905.38		$987.1283	$987.13	$987.15	$987.10