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	$58.53	4.658%	$61.2563	$61.26	$61.25	$61.30
Purchase #2	$105.31	13.426%	$119.4489	$119.45	$119.45	$119.40
Purchase #3	$97.86	13.509%	$111.0799	$111.08	$111.10	$111.10
Purchase #4	$171.76	13.474%	$194.9029	$194.90	$194.90	$194.90
Purchase #5	$218.72	10.857%	$242.4664	$242.47	$242.45	$242.50
Purchase #6	$33.76	8.150%	$36.5114	$36.51	$36.50	$36.50
Purchase #7	$49.53	9.187%	$54.0803	$54.08	$54.10	$54.10
7 purchase totals =	$735.47		$819.7461	$819.75	$819.75	$819.80