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	$131.30	8.272%	$142.1611	$142.16	$142.15	$142.20
Purchase #2	$45.34	7.826%	$48.8883	$48.89	$48.90	$48.90
Purchase #3	$212.80	12.223%	$238.8105	$238.81	$238.80	$238.80
Purchase #4	$183.45	7.141%	$196.5502	$196.55	$196.55	$196.60
Purchase #5	$154.55	12.231%	$173.453	$173.45	$173.45	$173.50
Purchase #6	$24.58	11.677%	$27.4502	$27.45	$27.45	$27.50
Purchase #7	$165.93	4.634%	$173.6192	$173.62	$173.60	$173.60
7 purchase totals =	$917.95		$1,000.9325	$1,000.93	$1,000.90	$1,001.10