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	$106.64	10.304%	$117.6282	$117.63	$117.65	$117.60
Purchase #2	$155.98	13.296%	$176.7191	$176.72	$176.70	$176.70
Purchase #3	$132.82	5.171%	$139.6881	$139.69	$139.70	$139.70
Purchase #4	$174.49	10.799%	$193.3332	$193.33	$193.35	$193.30
Purchase #5	$45.98	13.791%	$52.3211	$52.32	$52.30	$52.30
Purchase #6	$74.28	11.654%	$82.9366	$82.94	$82.95	$82.90
Purchase #7	$223.90	13.604%	$254.3594	$254.36	$254.35	$254.40
7 purchase totals =	$914.09		$1,016.9857	$1,016.99	$1,017.00	$1,016.90