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	$57.70	6.510%	$61.4563	$61.46	$61.45	$61.50
Purchase #2	$179.89	11.620%	$200.7932	$200.79	$200.80	$200.80
Purchase #3	$209.45	7.372%	$224.8907	$224.89	$224.90	$224.90
Purchase #4	$21.61	10.208%	$23.8159	$23.82	$23.80	$23.80
Purchase #5	$220.62	8.168%	$238.6402	$238.64	$238.65	$238.60
Purchase #6	$47.90	8.822%	$52.1257	$52.13	$52.15	$52.10
Purchase #7	$13.87	3.246%	$14.3202	$14.32	$14.30	$14.30
7 purchase totals =	$751.04		$816.0422	$816.05	$816.05	$816.00