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	$189.41	8.172%	$204.8886	$204.89	$204.90	$204.90
Purchase #2	$174.39	4.549%	$182.323	$182.32	$182.30	$182.30
Purchase #3	$144.30	12.308%	$162.0604	$162.06	$162.05	$162.10
Purchase #4	$237.61	5.208%	$249.9847	$249.98	$250.00	$250.00
Purchase #5	$60.72	9.436%	$66.4495	$66.45	$66.45	$66.40
Purchase #6	$106.87	12.709%	$120.4521	$120.45	$120.45	$120.50
Purchase #7	$41.51	6.609%	$44.2534	$44.25	$44.25	$44.30
7 purchase totals =	$954.81		$1,030.4117	$1,030.40	$1,030.40	$1,030.50