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	$44.81	7.178%	$48.0265	$48.03	$48.05	$48.00
Purchase #2	$129.87	12.600%	$146.2336	$146.23	$146.25	$146.20
Purchase #3	$23.31	11.109%	$25.8995	$25.90	$25.90	$25.90
Purchase #4	$194.66	13.257%	$220.4661	$220.47	$220.45	$220.50
Purchase #5	$177.39	7.416%	$190.5452	$190.55	$190.55	$190.50
Purchase #6	$105.39	3.867%	$109.4654	$109.47	$109.45	$109.50
Purchase #7	$43.40	5.207%	$45.6598	$45.66	$45.65	$45.70
7 purchase totals =	$718.83		$786.2961	$786.31	$786.30	$786.30