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	$80.95	3.562%	$83.8334	$83.83	$83.85	$83.80
Purchase #2	$62.84	12.651%	$70.7899	$70.79	$70.80	$70.80
Purchase #3	$57.25	9.324%	$62.588	$62.59	$62.60	$62.60
Purchase #4	$165.72	6.556%	$176.5846	$176.58	$176.60	$176.60
Purchase #5	$35.76	13.752%	$40.6777	$40.68	$40.70	$40.70
Purchase #6	$179.86	11.567%	$200.6644	$200.66	$200.65	$200.70
Purchase #7	$139.65	9.527%	$152.9545	$152.95	$152.95	$153.00
7 purchase totals =	$722.03		$788.0925	$788.08	$788.15	$788.20