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	$78.35	6.661%	$83.5689	$83.57	$83.55	$83.60
Purchase #2	$66.53	7.171%	$71.3009	$71.30	$71.30	$71.30
Purchase #3	$44.31	9.362%	$48.4583	$48.46	$48.45	$48.50
Purchase #4	$23.93	11.524%	$26.6877	$26.69	$26.70	$26.70
Purchase #5	$103.55	13.521%	$117.551	$117.55	$117.55	$117.60
Purchase #6	$176.37	11.667%	$196.9471	$196.95	$196.95	$196.90
Purchase #7	$216.46	11.626%	$241.6256	$241.63	$241.65	$241.60
7 purchase totals =	$709.50		$786.1395	$786.15	$786.15	$786.20