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	$143.59	8.802%	$156.2288	$156.23	$156.25	$156.20
Purchase #2	$54.27	3.261%	$56.0397	$56.04	$56.05	$56.00
Purchase #3	$95.81	10.159%	$105.5433	$105.54	$105.55	$105.50
Purchase #4	$11.96	5.369%	$12.6021	$12.60	$12.60	$12.60
Purchase #5	$238.88	10.376%	$263.6662	$263.67	$263.65	$263.70
Purchase #6	$171.98	5.630%	$181.6625	$181.66	$181.65	$181.70
Purchase #7	$49.77	12.429%	$55.9559	$55.96	$55.95	$56.00
7 purchase totals =	$766.26		$831.6985	$831.70	$831.70	$831.70