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	$48.43	8.659%	$52.6236	$52.62	$52.60	$52.60
Purchase #2	$34.30	12.163%	$38.4719	$38.47	$38.45	$38.50
Purchase #3	$244.90	5.803%	$259.1115	$259.11	$259.10	$259.10
Purchase #4	$162.89	13.352%	$184.6391	$184.64	$184.65	$184.60
Purchase #5	$124.80	5.264%	$131.3695	$131.37	$131.35	$131.40
Purchase #6	$140.83	7.764%	$151.764	$151.76	$151.75	$151.80
Purchase #7	$160.99	4.460%	$168.1702	$168.17	$168.15	$168.20
7 purchase totals =	$917.14		$986.1498	$986.14	$986.05	$986.20