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	$160.66	11.220%	$178.6861	$178.69	$178.70	$178.70
Purchase #2	$31.39	3.494%	$32.4868	$32.49	$32.50	$32.50
Purchase #3	$34.41	8.299%	$37.2657	$37.27	$37.25	$37.30
Purchase #4	$23.27	4.526%	$24.3232	$24.32	$24.30	$24.30
Purchase #5	$56.87	4.376%	$59.3586	$59.36	$59.35	$59.40
Purchase #6	$196.63	9.685%	$215.6736	$215.67	$215.65	$215.70
Purchase #7	$148.38	6.200%	$157.5796	$157.58	$157.60	$157.60
7 purchase totals =	$651.61		$705.3736	$705.38	$705.35	$705.50