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	$153.78	5.679%	$162.5132	$162.51	$162.50	$162.50
Purchase #2	$7.30	7.599%	$7.8547	$7.85	$7.85	$7.90
Purchase #3	$109.71	12.767%	$123.7167	$123.72	$123.70	$123.70
Purchase #4	$238.96	11.389%	$266.1752	$266.18	$266.20	$266.20
Purchase #5	$59.68	11.298%	$66.4226	$66.42	$66.40	$66.40
Purchase #6	$172.48	4.834%	$180.8177	$180.82	$180.80	$180.80
Purchase #7	$72.72	3.212%	$75.0558	$75.06	$75.05	$75.10
7 purchase totals =	$814.63		$882.5559	$882.56	$882.50	$882.60