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	$70.45	11.196%	$78.3376	$78.34	$78.35	$78.30
Purchase #2	$139.63	3.251%	$144.1694	$144.17	$144.15	$144.20
Purchase #3	$213.26	13.631%	$242.3295	$242.33	$242.35	$242.30
Purchase #4	$178.40	8.651%	$193.8334	$193.83	$193.85	$193.80
Purchase #5	$60.52	10.622%	$66.9484	$66.95	$66.95	$66.90
Purchase #6	$72.77	12.659%	$81.982	$81.98	$82.00	$82.00
Purchase #7	$197.74	12.572%	$222.5999	$222.60	$222.60	$222.60
7 purchase totals =	$932.77		$1,030.2002	$1,030.20	$1,030.25	$1,030.10