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	$159.65	5.727%	$168.7932	$168.79	$168.80	$168.80
Purchase #2	$89.70	12.555%	$100.9618	$100.96	$100.95	$101.00
Purchase #3	$21.51	3.539%	$22.2712	$22.27	$22.25	$22.30
Purchase #4	$34.91	7.159%	$37.4092	$37.41	$37.40	$37.40
Purchase #5	$93.62	5.790%	$99.0406	$99.04	$99.05	$99.00
Purchase #6	$192.63	13.412%	$218.4655	$218.47	$218.45	$218.50
Purchase #7	$126.91	4.506%	$132.6286	$132.63	$132.65	$132.60
7 purchase totals =	$718.93		$779.5701	$779.57	$779.55	$779.60