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	$49.45	6.336%	$52.5832	$52.58	$52.60	$52.60
Purchase #2	$104.87	5.511%	$110.6494	$110.65	$110.65	$110.60
Purchase #3	$247.75	13.206%	$280.4679	$280.47	$280.45	$280.50
Purchase #4	$94.78	11.282%	$105.4731	$105.47	$105.45	$105.50
Purchase #5	$212.67	9.740%	$233.3841	$233.38	$233.40	$233.40
Purchase #6	$121.46	13.632%	$138.0174	$138.02	$138.00	$138.00
Purchase #7	$134.58	10.113%	$148.1901	$148.19	$148.20	$148.20
7 purchase totals =	$965.56		$1,068.7652	$1,068.76	$1,068.75	$1,068.80