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	$64.77	9.381%	$70.8461	$70.85	$70.85	$70.80
Purchase #2	$100.79	10.453%	$111.3256	$111.33	$111.35	$111.30
Purchase #3	$123.47	12.330%	$138.6939	$138.69	$138.70	$138.70
Purchase #4	$94.80	10.809%	$105.0469	$105.05	$105.05	$105.00
Purchase #5	$213.31	10.118%	$234.8927	$234.89	$234.90	$234.90
Purchase #6	$213.97	8.135%	$231.3765	$231.38	$231.40	$231.40
Purchase #7	$168.39	4.196%	$175.4556	$175.46	$175.45	$175.50
7 purchase totals =	$979.50		$1,067.6373	$1,067.65	$1,067.70	$1,067.60