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	$233.53	10.495%	$258.039	$258.04	$258.05	$258.00
Purchase #2	$52.90	7.112%	$56.6622	$56.66	$56.65	$56.70
Purchase #3	$103.30	4.507%	$107.9557	$107.96	$107.95	$108.00
Purchase #4	$138.61	12.843%	$156.4117	$156.41	$156.40	$156.40
Purchase #5	$153.45	7.773%	$165.3777	$165.38	$165.40	$165.40
Purchase #6	$76.40	3.307%	$78.9265	$78.93	$78.95	$78.90
Purchase #7	$77.51	7.129%	$83.0357	$83.04	$83.05	$83.00
7 purchase totals =	$835.70		$906.4085	$906.42	$906.45	$906.40