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	$234.56	13.646%	$266.5681	$266.57	$266.55	$266.60
Purchase #2	$78.59	4.766%	$82.3356	$82.34	$82.35	$82.30
Purchase #3	$68.25	10.491%	$75.4101	$75.41	$75.40	$75.40
Purchase #4	$78.31	6.340%	$83.2749	$83.27	$83.25	$83.30
Purchase #5	$181.83	4.368%	$189.7723	$189.77	$189.75	$189.80
Purchase #6	$59.90	4.257%	$62.4499	$62.45	$62.45	$62.40
Purchase #7	$60.93	7.132%	$65.2755	$65.28	$65.30	$65.30
7 purchase totals =	$762.37		$825.0864	$825.09	$825.05	$825.10