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	$245.41	5.104%	$257.9357	$257.94	$257.95	$257.90
Purchase #2	$224.64	10.348%	$247.8857	$247.89	$247.90	$247.90
Purchase #3	$6.63	4.107%	$6.9023	$6.90	$6.90	$6.90
Purchase #4	$11.71	5.416%	$12.3442	$12.34	$12.35	$12.30
Purchase #5	$229.45	8.742%	$249.5085	$249.51	$249.50	$249.50
Purchase #6	$80.75	11.107%	$89.7189	$89.72	$89.70	$89.70
Purchase #7	$40.56	7.510%	$43.6061	$43.61	$43.60	$43.60
7 purchase totals =	$839.15		$907.9014	$907.91	$907.90	$907.80