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	$95.53	8.130%	$103.2966	$103.30	$103.30	$103.30
Purchase #2	$147.90	4.196%	$154.1059	$154.11	$154.10	$154.10
Purchase #3	$18.65	12.491%	$20.9796	$20.98	$21.00	$21.00
Purchase #4	$38.78	11.262%	$43.1474	$43.15	$43.15	$43.10
Purchase #5	$144.25	4.631%	$150.9302	$150.93	$150.95	$150.90
Purchase #6	$70.25	9.391%	$76.8472	$76.85	$76.85	$76.80
Purchase #7	$159.59	10.468%	$176.2959	$176.30	$176.30	$176.30
7 purchase totals =	$674.95		$725.6028	$725.62	$725.65	$725.50