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	$76.66	13.172%	$86.7577	$86.76	$86.75	$86.80
Purchase #2	$25.41	7.471%	$27.3084	$27.31	$27.30	$27.30
Purchase #3	$81.29	10.130%	$89.5247	$89.52	$89.50	$89.50
Purchase #4	$118.56	7.633%	$127.6097	$127.61	$127.60	$127.60
Purchase #5	$210.81	4.386%	$220.0561	$220.06	$220.05	$220.10
Purchase #6	$157.87	4.456%	$164.9047	$164.90	$164.90	$164.90
Purchase #7	$227.38	5.715%	$240.3748	$240.37	$240.35	$240.40
7 purchase totals =	$897.98		$956.5361	$956.53	$956.45	$956.60