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	$127.52	3.487%	$131.9666	$131.97	$131.95	$132.00
Purchase #2	$128.77	13.141%	$145.6917	$145.69	$145.70	$145.70
Purchase #3	$97.36	8.715%	$105.8449	$105.84	$105.85	$105.80
Purchase #4	$250.32	9.752%	$274.7312	$274.73	$274.75	$274.70
Purchase #5	$144.80	4.389%	$151.1553	$151.16	$151.15	$151.20
Purchase #6	$17.74	13.454%	$20.1267	$20.13	$20.15	$20.10
Purchase #7	$70.83	8.756%	$77.0319	$77.03	$77.05	$77.00
7 purchase totals =	$837.34		$906.5483	$906.55	$906.60	$906.50