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	$153.47	6.375%	$163.2537	$163.25	$163.25	$163.30
Purchase #2	$6.54	4.254%	$6.8182	$6.82	$6.80	$6.80
Purchase #3	$128.78	6.614%	$137.2975	$137.30	$137.30	$137.30
Purchase #4	$204.36	11.841%	$228.5583	$228.56	$228.55	$228.60
Purchase #5	$118.51	11.218%	$131.8045	$131.80	$131.80	$131.80
Purchase #6	$144.52	5.307%	$152.1897	$152.19	$152.20	$152.20
Purchase #7	$179.91	9.274%	$196.5949	$196.59	$196.60	$196.60
7 purchase totals =	$936.09		$1,016.5168	$1,016.51	$1,016.50	$1,016.60