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	$103.82	9.223%	$113.3953	$113.40	$113.40	$113.40
Purchase #2	$18.47	5.586%	$19.5017	$19.50	$19.50	$19.50
Purchase #3	$7.99	7.757%	$8.6098	$8.61	$8.60	$8.60
Purchase #4	$141.34	12.142%	$158.5015	$158.50	$158.50	$158.50
Purchase #5	$239.28	4.854%	$250.8947	$250.89	$250.90	$250.90
Purchase #6	$137.73	3.467%	$142.5051	$142.51	$142.50	$142.50
Purchase #7	$190.34	11.196%	$211.6505	$211.65	$211.65	$211.70
7 purchase totals =	$838.97		$905.0586	$905.06	$905.05	$905.10