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	$120.62	3.698%	$125.0805	$125.08	$125.10	$125.10
Purchase #2	$90.54	11.408%	$100.8688	$100.87	$100.85	$100.90
Purchase #3	$210.32	5.654%	$222.2115	$222.21	$222.20	$222.20
Purchase #4	$86.51	4.771%	$90.6374	$90.64	$90.65	$90.60
Purchase #5	$122.46	13.167%	$138.5843	$138.58	$138.60	$138.60
Purchase #6	$155.64	4.229%	$162.222	$162.22	$162.20	$162.20
Purchase #7	$152.76	10.153%	$168.2697	$168.27	$168.25	$168.30
7 purchase totals =	$938.85		$1,007.8742	$1,007.87	$1,007.85	$1,007.90