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	$117.98	8.776%	$128.3339	$128.33	$128.35	$128.30
Purchase #2	$190.74	4.308%	$198.9571	$198.96	$198.95	$199.00
Purchase #3	$19.28	11.766%	$21.5485	$21.55	$21.55	$21.50
Purchase #4	$106.54	4.522%	$111.3577	$111.36	$111.35	$111.40
Purchase #5	$135.87	4.702%	$142.2586	$142.26	$142.25	$142.30
Purchase #6	$106.97	3.409%	$110.6166	$110.62	$110.60	$110.60
Purchase #7	$144.54	12.694%	$162.8879	$162.89	$162.90	$162.90
7 purchase totals =	$821.92		$875.9603	$875.97	$875.95	$876.00