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	$177.80	12.744%	$200.4588	$200.46	$200.45	$200.50
Purchase #2	$86.37	4.183%	$89.9829	$89.98	$90.00	$90.00
Purchase #3	$227.52	10.521%	$251.4574	$251.46	$251.45	$251.50
Purchase #4	$89.29	5.258%	$93.9849	$93.98	$94.00	$94.00
Purchase #5	$196.77	10.697%	$217.8185	$217.82	$217.80	$217.80
Purchase #6	$9.52	12.541%	$10.7139	$10.71	$10.70	$10.70
Purchase #7	$100.87	11.179%	$112.1463	$112.15	$112.15	$112.10
7 purchase totals =	$888.14		$976.5627	$976.56	$976.55	$976.60