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	$184.86	6.293%	$196.4932	$196.49	$196.50	$196.50
Purchase #2	$247.49	13.528%	$280.9704	$280.97	$280.95	$281.00
Purchase #3	$118.37	12.740%	$133.4503	$133.45	$133.45	$133.50
Purchase #4	$122.81	11.692%	$137.1689	$137.17	$137.15	$137.20
Purchase #5	$157.95	5.437%	$166.5377	$166.54	$166.55	$166.50
Purchase #6	$123.98	5.472%	$130.7642	$130.76	$130.75	$130.80
Purchase #7	$188.54	8.430%	$204.4339	$204.43	$204.45	$204.40
7 purchase totals =	$1,144.00		$1,249.8186	$1,249.81	$1,249.80	$1,249.90