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	$238.79	5.439%	$251.7778	$251.78	$251.80	$251.80
Purchase #2	$250.59	5.417%	$264.1645	$264.16	$264.15	$264.20
Purchase #3	$61.60	8.582%	$66.8865	$66.89	$66.90	$66.90
Purchase #4	$173.39	4.303%	$180.851	$180.85	$180.85	$180.90
Purchase #5	$172.95	9.641%	$189.6241	$189.62	$189.60	$189.60
Purchase #6	$67.45	10.176%	$74.3137	$74.31	$74.30	$74.30
Purchase #7	$115.82	10.538%	$128.0251	$128.03	$128.05	$128.00
7 purchase totals =	$1,080.59		$1,155.6427	$1,155.64	$1,155.65	$1,155.70