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	$86.88	4.550%	$90.833	$90.83	$90.85	$90.80
Purchase #2	$33.61	6.535%	$35.8064	$35.81	$35.80	$35.80
Purchase #3	$130.97	9.519%	$143.437	$143.44	$143.45	$143.40
Purchase #4	$75.78	5.822%	$80.1919	$80.19	$80.20	$80.20
Purchase #5	$16.89	13.500%	$19.1702	$19.17	$19.15	$19.20
Purchase #6	$144.58	5.776%	$152.9309	$152.93	$152.95	$152.90
Purchase #7	$235.63	12.713%	$265.5856	$265.59	$265.60	$265.60
7 purchase totals =	$724.34		$787.9550	$787.96	$788.00	$787.90