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	$64.63	12.636%	$72.7966	$72.80	$72.80	$72.80
Purchase #2	$49.30	10.551%	$54.5016	$54.50	$54.50	$54.50
Purchase #3	$136.65	7.145%	$146.4136	$146.41	$146.40	$146.40
Purchase #4	$190.61	12.641%	$214.705	$214.71	$214.70	$214.70
Purchase #5	$23.60	9.424%	$25.8241	$25.82	$25.80	$25.80
Purchase #6	$19.33	10.277%	$21.3165	$21.32	$21.30	$21.30
Purchase #7	$65.66	9.293%	$71.7618	$71.76	$71.75	$71.80
7 purchase totals =	$549.78		$607.3192	$607.32	$607.25	$607.30