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	$96.62	9.568%	$105.8646	$105.86	$105.85	$105.90
Purchase #2	$216.76	4.222%	$225.9116	$225.91	$225.90	$225.90
Purchase #3	$37.36	4.266%	$38.9538	$38.95	$38.95	$39.00
Purchase #4	$9.54	12.267%	$10.7103	$10.71	$10.70	$10.70
Purchase #5	$25.83	10.356%	$28.505	$28.51	$28.50	$28.50
Purchase #6	$36.78	11.706%	$41.0855	$41.09	$41.10	$41.10
Purchase #7	$103.50	11.589%	$115.4946	$115.49	$115.50	$115.50
7 purchase totals =	$526.39		$566.5254	$566.52	$566.50	$566.60