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	$217.60	10.604%	$240.6743	$240.67	$240.65	$240.70
Purchase #2	$238.45	13.362%	$270.3117	$270.31	$270.30	$270.30
Purchase #3	$101.93	3.574%	$105.573	$105.57	$105.55	$105.60
Purchase #4	$115.61	9.519%	$126.6149	$126.61	$126.60	$126.60
Purchase #5	$61.76	4.330%	$64.4342	$64.43	$64.45	$64.40
Purchase #6	$220.89	9.685%	$242.2832	$242.28	$242.30	$242.30
Purchase #7	$49.37	11.449%	$55.0224	$55.02	$55.00	$55.00
7 purchase totals =	$1,005.61		$1,104.9137	$1,104.89	$1,104.85	$1,104.90