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	$63.67	5.199%	$66.9802	$66.98	$67.00	$67.00
Purchase #2	$95.59	5.164%	$100.5263	$100.53	$100.55	$100.50
Purchase #3	$72.54	7.208%	$77.7687	$77.77	$77.75	$77.80
Purchase #4	$218.27	10.601%	$241.4088	$241.41	$241.40	$241.40
Purchase #5	$163.52	5.255%	$172.113	$172.11	$172.10	$172.10
Purchase #6	$188.26	6.431%	$200.367	$200.37	$200.35	$200.40
Purchase #7	$116.48	7.154%	$124.813	$124.81	$124.80	$124.80
7 purchase totals =	$918.33		$983.9770	$983.98	$983.95	$984.00