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	$124.83	6.236%	$132.6144	$132.61	$132.60	$132.60
Purchase #2	$19.53	7.154%	$20.9272	$20.93	$20.95	$20.90
Purchase #3	$65.32	8.449%	$70.8389	$70.84	$70.85	$70.80
Purchase #4	$64.91	11.189%	$72.1728	$72.17	$72.15	$72.20
Purchase #5	$44.98	13.332%	$50.9767	$50.98	$51.00	$51.00
Purchase #6	$155.61	11.870%	$174.0809	$174.08	$174.10	$174.10
Purchase #7	$196.86	5.736%	$208.1519	$208.15	$208.15	$208.20
7 purchase totals =	$672.04		$729.7628	$729.76	$729.80	$729.80