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	$152.98	8.581%	$166.1072	$166.11	$166.10	$166.10
Purchase #2	$11.31	9.531%	$12.388	$12.39	$12.40	$12.40
Purchase #3	$97.32	6.102%	$103.2585	$103.26	$103.25	$103.30
Purchase #4	$48.70	5.836%	$51.5421	$51.54	$51.55	$51.50
Purchase #5	$160.86	5.838%	$170.251	$170.25	$170.25	$170.30
Purchase #6	$37.59	13.838%	$42.7917	$42.79	$42.80	$42.80
Purchase #7	$52.36	10.480%	$57.8473	$57.85	$57.85	$57.80
7 purchase totals =	$561.12		$604.1858	$604.19	$604.20	$604.20