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	$205.54	8.521%	$223.0541	$223.05	$223.05	$223.10
Purchase #2	$158.62	11.198%	$176.3823	$176.38	$176.40	$176.40
Purchase #3	$240.26	5.334%	$253.0755	$253.08	$253.10	$253.10
Purchase #4	$38.27	10.530%	$42.2998	$42.30	$42.30	$42.30
Purchase #5	$187.58	4.730%	$196.4525	$196.45	$196.45	$196.50
Purchase #6	$65.31	10.835%	$72.3863	$72.39	$72.40	$72.40
Purchase #7	$93.63	7.376%	$100.5361	$100.54	$100.55	$100.50
7 purchase totals =	$989.21		$1,064.1866	$1,064.19	$1,064.25	$1,064.30