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	$48.32	9.264%	$52.7964	$52.80	$52.80	$52.80
Purchase #2	$243.65	5.361%	$256.7121	$256.71	$256.70	$256.70
Purchase #3	$138.67	4.352%	$144.7049	$144.70	$144.70	$144.70
Purchase #4	$185.93	11.612%	$207.5202	$207.52	$207.50	$207.50
Purchase #5	$79.42	11.470%	$88.5295	$88.53	$88.55	$88.50
Purchase #6	$105.30	6.128%	$111.7528	$111.75	$111.75	$111.80
Purchase #7	$144.42	12.518%	$162.4985	$162.50	$162.50	$162.50
7 purchase totals =	$945.71		$1,024.5144	$1,024.51	$1,024.50	$1,024.50