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	$57.73	9.535%	$63.2346	$63.23	$63.25	$63.20
Purchase #2	$129.77	5.703%	$137.1708	$137.17	$137.15	$137.20
Purchase #3	$135.95	5.464%	$143.3783	$143.38	$143.40	$143.40
Purchase #4	$69.64	5.386%	$73.3908	$73.39	$73.40	$73.40
Purchase #5	$52.32	13.395%	$59.3283	$59.33	$59.35	$59.30
Purchase #6	$159.70	8.552%	$173.3575	$173.36	$173.35	$173.40
Purchase #7	$59.43	5.217%	$62.5305	$62.53	$62.55	$62.50
7 purchase totals =	$664.54		$712.3908	$712.39	$712.45	$712.40