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	$31.98	13.510%	$36.3005	$36.30	$36.30	$36.30
Purchase #2	$78.91	12.417%	$88.7083	$88.71	$88.70	$88.70
Purchase #3	$166.63	3.307%	$172.1405	$172.14	$172.15	$172.10
Purchase #4	$39.91	8.555%	$43.3243	$43.32	$43.30	$43.30
Purchase #5	$187.71	4.788%	$196.6976	$196.70	$196.70	$196.70
Purchase #6	$125.50	11.613%	$140.0743	$140.07	$140.05	$140.10
Purchase #7	$49.53	10.252%	$54.6078	$54.61	$54.60	$54.60
7 purchase totals =	$680.17		$731.8533	$731.85	$731.80	$731.80