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	$208.90	6.344%	$222.1526	$222.15	$222.15	$222.20
Purchase #2	$38.76	6.261%	$41.1868	$41.19	$41.20	$41.20
Purchase #3	$34.76	12.437%	$39.0831	$39.08	$39.10	$39.10
Purchase #4	$217.33	12.827%	$245.2069	$245.21	$245.20	$245.20
Purchase #5	$148.58	12.703%	$167.4541	$167.45	$167.45	$167.50
Purchase #6	$237.48	3.430%	$245.6256	$245.63	$245.65	$245.60
Purchase #7	$92.96	7.643%	$100.0649	$100.06	$100.05	$100.10
7 purchase totals =	$978.77		$1,060.7740	$1,060.77	$1,060.80	$1,060.90