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	$169.33	7.785%	$182.5123	$182.51	$182.50	$182.50
Purchase #2	$208.97	4.851%	$219.1071	$219.11	$219.10	$219.10
Purchase #3	$211.47	5.209%	$222.4855	$222.49	$222.50	$222.50
Purchase #4	$183.55	12.115%	$205.7871	$205.79	$205.80	$205.80
Purchase #5	$105.57	10.757%	$116.9262	$116.93	$116.95	$116.90
Purchase #6	$39.83	8.314%	$43.1415	$43.14	$43.15	$43.10
Purchase #7	$74.48	4.248%	$77.6439	$77.64	$77.65	$77.60
7 purchase totals =	$993.20		$1,067.6036	$1,067.61	$1,067.65	$1,067.50