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	$157.59	9.642%	$172.7848	$172.78	$172.80	$172.80
Purchase #2	$141.86	10.583%	$156.873	$156.87	$156.85	$156.90
Purchase #3	$40.57	11.686%	$45.311	$45.31	$45.30	$45.30
Purchase #4	$175.27	8.653%	$190.4361	$190.44	$190.45	$190.40
Purchase #5	$29.50	11.792%	$32.9786	$32.98	$33.00	$33.00
Purchase #6	$163.78	5.668%	$173.0631	$173.06	$173.05	$173.10
Purchase #7	$176.46	11.593%	$196.917	$196.92	$196.90	$196.90
7 purchase totals =	$885.03		$968.3636	$968.36	$968.35	$968.40