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	$39.96	12.480%	$44.947	$44.95	$44.95	$44.90
Purchase #2	$246.81	8.380%	$267.4927	$267.49	$267.50	$267.50
Purchase #3	$99.63	11.469%	$111.0566	$111.06	$111.05	$111.10
Purchase #4	$24.74	3.172%	$25.5248	$25.52	$25.50	$25.50
Purchase #5	$52.60	7.385%	$56.4845	$56.48	$56.50	$56.50
Purchase #6	$101.71	6.461%	$108.2815	$108.28	$108.30	$108.30
Purchase #7	$56.93	5.316%	$59.9564	$59.96	$59.95	$60.00
7 purchase totals =	$622.38		$673.7435	$673.74	$673.75	$673.80