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	$16.39	5.772%	$17.336	$17.34	$17.35	$17.30
Purchase #2	$6.65	6.335%	$7.0713	$7.07	$7.05	$7.10
Purchase #3	$5.70	13.322%	$6.4594	$6.46	$6.45	$6.50
Purchase #4	$205.71	10.207%	$226.7068	$226.71	$226.70	$226.70
Purchase #5	$91.69	9.624%	$100.5142	$100.51	$100.50	$100.50
Purchase #6	$143.59	9.248%	$156.8692	$156.87	$156.85	$156.90
Purchase #7	$73.77	11.761%	$82.4461	$82.45	$82.45	$82.40
7 purchase totals =	$543.50		$597.4030	$597.41	$597.35	$597.40