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	$155.64	13.546%	$176.723	$176.72	$176.70	$176.70
Purchase #2	$204.89	5.738%	$216.6466	$216.65	$216.65	$216.60
Purchase #3	$43.38	4.534%	$45.3468	$45.35	$45.35	$45.30
Purchase #4	$87.25	13.543%	$99.0663	$99.07	$99.05	$99.10
Purchase #5	$153.74	8.222%	$166.3805	$166.38	$166.40	$166.40
Purchase #6	$63.61	3.729%	$65.982	$65.98	$66.00	$66.00
Purchase #7	$240.27	7.502%	$258.2951	$258.30	$258.30	$258.30
7 purchase totals =	$948.78		$1,028.4403	$1,028.45	$1,028.45	$1,028.40