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	$97.30	8.462%	$105.5335	$105.53	$105.55	$105.50
Purchase #2	$109.45	9.276%	$119.6026	$119.60	$119.60	$119.60
Purchase #3	$14.35	9.526%	$15.717	$15.72	$15.70	$15.70
Purchase #4	$48.27	11.365%	$53.7559	$53.76	$53.75	$53.80
Purchase #5	$169.83	7.598%	$182.7337	$182.73	$182.75	$182.70
Purchase #6	$37.34	3.506%	$38.6491	$38.65	$38.65	$38.60
Purchase #7	$13.67	13.540%	$15.5209	$15.52	$15.50	$15.50
7 purchase totals =	$490.21		$531.5127	$531.51	$531.50	$531.40