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	$131.33	9.263%	$143.4951	$143.50	$143.50	$143.50
Purchase #2	$91.72	9.668%	$100.5875	$100.59	$100.60	$100.60
Purchase #3	$31.64	10.705%	$35.0271	$35.03	$35.05	$35.00
Purchase #4	$49.90	4.753%	$52.2717	$52.27	$52.25	$52.30
Purchase #5	$35.71	8.388%	$38.7054	$38.71	$38.70	$38.70
Purchase #6	$233.65	12.541%	$262.952	$262.95	$262.95	$263.00
Purchase #7	$57.74	5.502%	$60.9169	$60.92	$60.90	$60.90
7 purchase totals =	$631.69		$693.9557	$693.97	$693.95	$694.00