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	$54.37	4.110%	$56.6046	$56.60	$56.60	$56.60
Purchase #2	$11.95	7.672%	$12.8668	$12.87	$12.85	$12.90
Purchase #3	$122.77	3.767%	$127.3947	$127.39	$127.40	$127.40
Purchase #4	$203.76	3.321%	$210.5269	$210.53	$210.55	$210.50
Purchase #5	$74.81	4.419%	$78.1159	$78.12	$78.10	$78.10
Purchase #6	$133.93	7.450%	$143.9078	$143.91	$143.90	$143.90
Purchase #7	$90.48	13.336%	$102.5464	$102.55	$102.55	$102.50
7 purchase totals =	$692.07		$731.9631	$731.97	$731.95	$731.90