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	$196.75	11.839%	$220.0432	$220.04	$220.05	$220.00
Purchase #2	$47.33	13.625%	$53.7787	$53.78	$53.80	$53.80
Purchase #3	$113.92	8.329%	$123.4084	$123.41	$123.40	$123.40
Purchase #4	$13.49	9.117%	$14.7199	$14.72	$14.70	$14.70
Purchase #5	$168.78	6.559%	$179.8503	$179.85	$179.85	$179.90
Purchase #6	$228.95	5.330%	$241.153	$241.15	$241.15	$241.20
Purchase #7	$235.28	3.721%	$244.0348	$244.03	$244.05	$244.00
7 purchase totals =	$1,004.50		$1,076.9883	$1,076.98	$1,077.00	$1,077.00