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	$85.25	10.618%	$94.3018	$94.30	$94.30	$94.30
Purchase #2	$94.48	10.810%	$104.6933	$104.69	$104.70	$104.70
Purchase #3	$164.87	10.202%	$181.69	$181.69	$181.70	$181.70
Purchase #4	$52.59	3.413%	$54.3849	$54.38	$54.40	$54.40
Purchase #5	$127.70	3.117%	$131.6804	$131.68	$131.70	$131.70
Purchase #6	$17.35	5.693%	$18.3377	$18.34	$18.35	$18.30
Purchase #7	$18.46	12.663%	$20.7976	$20.80	$20.80	$20.80
7 purchase totals =	$560.70		$605.8857	$605.88	$605.95	$605.90