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	$146.61	5.684%	$154.9433	$154.94	$154.95	$154.90
Purchase #2	$55.36	4.261%	$57.7189	$57.72	$57.70	$57.70
Purchase #3	$34.38	9.770%	$37.7389	$37.74	$37.75	$37.70
Purchase #4	$101.78	9.174%	$111.1173	$111.12	$111.10	$111.10
Purchase #5	$80.92	11.682%	$90.3731	$90.37	$90.35	$90.40
Purchase #6	$148.52	5.701%	$156.9871	$156.99	$157.00	$157.00
Purchase #7	$177.96	11.277%	$198.0285	$198.03	$198.05	$198.00
7 purchase totals =	$745.53		$806.9071	$806.91	$806.90	$806.80