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	$151.55	10.196%	$167.002	$167.00	$167.00	$167.00
Purchase #2	$215.39	12.713%	$242.7725	$242.77	$242.75	$242.80
Purchase #3	$213.89	5.496%	$225.6454	$225.65	$225.65	$225.60
Purchase #4	$144.52	13.405%	$163.8929	$163.89	$163.90	$163.90
Purchase #5	$80.43	12.418%	$90.4178	$90.42	$90.40	$90.40
Purchase #6	$118.56	5.663%	$125.2741	$125.27	$125.25	$125.30
Purchase #7	$53.52	4.746%	$56.0601	$56.06	$56.05	$56.10
7 purchase totals =	$977.86		$1,071.0648	$1,071.06	$1,071.00	$1,071.10