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	$121.72	9.223%	$132.9462	$132.95	$132.95	$132.90
Purchase #2	$137.75	3.644%	$142.7696	$142.77	$142.75	$142.80
Purchase #3	$116.32	6.286%	$123.6319	$123.63	$123.65	$123.60
Purchase #4	$111.73	5.632%	$118.0226	$118.02	$118.00	$118.00
Purchase #5	$131.42	4.675%	$137.5639	$137.56	$137.55	$137.60
Purchase #6	$167.97	9.567%	$184.0397	$184.04	$184.05	$184.00
Purchase #7	$109.59	12.488%	$123.2756	$123.28	$123.30	$123.30
7 purchase totals =	$896.50		$962.2495	$962.25	$962.25	$962.20