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	$71.80	9.277%	$78.4609	$78.46	$78.45	$78.50
Purchase #2	$247.33	6.669%	$263.8244	$263.82	$263.80	$263.80
Purchase #3	$114.68	13.466%	$130.1228	$130.12	$130.10	$130.10
Purchase #4	$108.90	9.202%	$118.921	$118.92	$118.90	$118.90
Purchase #5	$144.51	10.423%	$159.5723	$159.57	$159.55	$159.60
Purchase #6	$32.25	11.419%	$35.9326	$35.93	$35.95	$35.90
Purchase #7	$148.27	5.548%	$156.496	$156.50	$156.50	$156.50
7 purchase totals =	$867.74		$943.3300	$943.32	$943.25	$943.30