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	$235.87	13.149%	$266.8845	$266.88	$266.90	$266.90
Purchase #2	$42.79	6.664%	$45.6415	$45.64	$45.65	$45.60
Purchase #3	$195.71	9.631%	$214.5588	$214.56	$214.55	$214.60
Purchase #4	$142.80	5.394%	$150.5026	$150.50	$150.50	$150.50
Purchase #5	$85.69	5.516%	$90.4167	$90.42	$90.40	$90.40
Purchase #6	$162.62	7.348%	$174.5693	$174.57	$174.55	$174.60
Purchase #7	$97.31	8.325%	$105.4111	$105.41	$105.40	$105.40
7 purchase totals =	$962.79		$1,047.9845	$1,047.98	$1,047.95	$1,048.00