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	$124.27	5.123%	$130.6364	$130.64	$130.65	$130.60
Purchase #2	$103.28	5.572%	$109.0348	$109.03	$109.05	$109.00
Purchase #3	$83.51	6.665%	$89.0759	$89.08	$89.10	$89.10
Purchase #4	$146.48	10.162%	$161.3653	$161.37	$161.35	$161.40
Purchase #5	$43.61	13.405%	$49.4559	$49.46	$49.45	$49.50
Purchase #6	$246.47	12.124%	$276.352	$276.35	$276.35	$276.40
Purchase #7	$216.89	3.549%	$224.5874	$224.59	$224.60	$224.60
7 purchase totals =	$964.51		$1,040.5077	$1,040.52	$1,040.55	$1,040.60