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	$197.82	5.278%	$208.2609	$208.26	$208.25	$208.30
Purchase #2	$77.93	7.221%	$83.5573	$83.56	$83.55	$83.60
Purchase #3	$120.55	9.821%	$132.3892	$132.39	$132.40	$132.40
Purchase #4	$136.94	3.590%	$141.8561	$141.86	$141.85	$141.90
Purchase #5	$172.60	4.749%	$180.7968	$180.80	$180.80	$180.80
Purchase #6	$159.91	4.217%	$166.6534	$166.65	$166.65	$166.70
Purchase #7	$96.49	8.845%	$105.0245	$105.02	$105.00	$105.00
7 purchase totals =	$962.24		$1,018.5382	$1,018.54	$1,018.50	$1,018.70