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	$106.95	9.166%	$116.753	$116.75	$116.75	$116.80
Purchase #2	$50.93	10.389%	$56.2211	$56.22	$56.20	$56.20
Purchase #3	$247.92	4.223%	$258.3897	$258.39	$258.40	$258.40
Purchase #4	$196.88	5.707%	$208.1159	$208.12	$208.10	$208.10
Purchase #5	$100.33	12.560%	$112.9314	$112.93	$112.95	$112.90
Purchase #6	$160.50	6.578%	$171.0577	$171.06	$171.05	$171.10
Purchase #7	$75.58	6.530%	$80.5154	$80.52	$80.50	$80.50
7 purchase totals =	$939.09		$1,003.9842	$1,003.99	$1,003.95	$1,004.00