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	$213.45	4.571%	$223.2068	$223.21	$223.20	$223.20
Purchase #2	$188.60	4.419%	$196.9342	$196.93	$196.95	$196.90
Purchase #3	$58.27	12.864%	$65.7659	$65.77	$65.75	$65.80
Purchase #4	$44.63	8.241%	$48.308	$48.31	$48.30	$48.30
Purchase #5	$120.52	5.158%	$126.7364	$126.74	$126.75	$126.70
Purchase #6	$72.92	6.392%	$77.581	$77.58	$77.60	$77.60
Purchase #7	$118.37	8.857%	$128.854	$128.85	$128.85	$128.90
7 purchase totals =	$816.76		$867.3863	$867.39	$867.40	$867.40