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	$16.38	6.510%	$17.4463	$17.45	$17.45	$17.40
Purchase #2	$146.99	3.721%	$152.4595	$152.46	$152.45	$152.50
Purchase #3	$243.62	8.731%	$264.8905	$264.89	$264.90	$264.90
Purchase #4	$142.25	6.477%	$151.4635	$151.46	$151.45	$151.50
Purchase #5	$152.66	10.102%	$168.0817	$168.08	$168.10	$168.10
Purchase #6	$163.95	5.355%	$172.7295	$172.73	$172.75	$172.70
Purchase #7	$150.51	5.651%	$159.0153	$159.02	$159.00	$159.00
7 purchase totals =	$1,016.36		$1,086.0863	$1,086.09	$1,086.10	$1,086.10