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	$43.75	6.222%	$46.4721	$46.47	$46.45	$46.50
Purchase #2	$164.34	10.285%	$181.2424	$181.24	$181.25	$181.20
Purchase #3	$61.40	6.282%	$65.2571	$65.26	$65.25	$65.30
Purchase #4	$38.83	13.498%	$44.0713	$44.07	$44.05	$44.10
Purchase #5	$32.64	9.405%	$35.7098	$35.71	$35.70	$35.70
Purchase #6	$7.55	5.538%	$7.9681	$7.97	$7.95	$8.00
Purchase #7	$56.39	9.185%	$61.5694	$61.57	$61.55	$61.60
7 purchase totals =	$404.90		$442.2902	$442.29	$442.20	$442.40