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	$86.28	4.163%	$89.8718	$89.87	$89.85	$89.90
Purchase #2	$201.62	12.327%	$226.4737	$226.47	$226.45	$226.50
Purchase #3	$85.61	8.582%	$92.9571	$92.96	$92.95	$93.00
Purchase #4	$138.38	7.492%	$148.7474	$148.75	$148.75	$148.70
Purchase #5	$62.70	7.852%	$67.6232	$67.62	$67.60	$67.60
Purchase #6	$62.29	8.363%	$67.4993	$67.50	$67.50	$67.50
Purchase #7	$76.47	5.399%	$80.5986	$80.60	$80.60	$80.60
7 purchase totals =	$713.35		$773.7711	$773.77	$773.70	$773.80