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	$40.83	4.412%	$42.6314	$42.63	$42.65	$42.60
Purchase #2	$118.43	11.574%	$132.1371	$132.14	$132.15	$132.10
Purchase #3	$208.57	5.435%	$219.9058	$219.91	$219.90	$219.90
Purchase #4	$171.48	7.580%	$184.4782	$184.48	$184.50	$184.50
Purchase #5	$153.29	13.152%	$173.4507	$173.45	$173.45	$173.50
Purchase #6	$100.72	3.215%	$103.9581	$103.96	$103.95	$104.00
Purchase #7	$228.75	5.797%	$242.0106	$242.01	$242.00	$242.00
7 purchase totals =	$1,022.07		$1,098.5719	$1,098.58	$1,098.60	$1,098.60