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	8.555%	$212.4638	$212.46	$212.45	$212.50
Purchase #2	$249.30	9.753%	$273.6142	$273.61	$273.60	$273.60
Purchase #3	$176.39	11.287%	$196.2991	$196.30	$196.30	$196.30
Purchase #4	$204.29	3.635%	$211.7159	$211.72	$211.70	$211.70
Purchase #5	$244.31	9.443%	$267.3802	$267.38	$267.40	$267.40
Purchase #6	$107.77	10.146%	$118.7043	$118.70	$118.70	$118.70
Purchase #7	$59.42	10.861%	$65.8736	$65.87	$65.85	$65.90
7 purchase totals =	$1,237.20		$1,346.0511	$1,346.04	$1,346.00	$1,346.10