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	$111.55	10.631%	$123.4089	$123.41	$123.40	$123.40
Purchase #2	$11.69	6.659%	$12.4684	$12.47	$12.45	$12.50
Purchase #3	$201.52	9.681%	$221.0292	$221.03	$221.05	$221.00
Purchase #4	$7.89	9.511%	$8.6404	$8.64	$8.65	$8.60
Purchase #5	$195.83	5.120%	$205.8565	$205.86	$205.85	$205.90
Purchase #6	$11.91	3.424%	$12.3178	$12.32	$12.30	$12.30
Purchase #7	$28.76	12.382%	$32.3211	$32.32	$32.30	$32.30
7 purchase totals =	$569.15		$616.0423	$616.05	$616.00	$616.00