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	$90.45	8.852%	$98.4566	$98.46	$98.45	$98.50
Purchase #2	$93.83	7.257%	$100.6392	$100.64	$100.65	$100.60
Purchase #3	$159.70	11.301%	$177.7477	$177.75	$177.75	$177.70
Purchase #4	$144.35	5.563%	$152.3802	$152.38	$152.40	$152.40
Purchase #5	$31.37	7.383%	$33.686	$33.69	$33.70	$33.70
Purchase #6	$153.29	7.495%	$164.7791	$164.78	$164.80	$164.80
Purchase #7	$168.72	12.107%	$189.1469	$189.15	$189.15	$189.10
7 purchase totals =	$841.71		$916.8357	$916.85	$916.90	$916.80