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	$149.38	9.462%	$163.5143	$163.51	$163.50	$163.50
Purchase #2	$7.45	12.633%	$8.3912	$8.39	$8.40	$8.40
Purchase #3	$38.85	8.487%	$42.1472	$42.15	$42.15	$42.10
Purchase #4	$240.66	13.682%	$273.5871	$273.59	$273.60	$273.60
Purchase #5	$60.98	13.563%	$69.2507	$69.25	$69.25	$69.30
Purchase #6	$77.46	10.739%	$85.7784	$85.78	$85.80	$85.80
Purchase #7	$166.56	4.362%	$173.8253	$173.83	$173.85	$173.80
7 purchase totals =	$741.34		$816.4942	$816.50	$816.55	$816.50