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	$19.34	6.272%	$20.553	$20.55	$20.55	$20.60
Purchase #2	$31.95	5.378%	$33.6683	$33.67	$33.65	$33.70
Purchase #3	$177.94	8.164%	$192.467	$192.47	$192.45	$192.50
Purchase #4	$180.39	5.483%	$190.2808	$190.28	$190.30	$190.30
Purchase #5	$250.39	10.847%	$277.5498	$277.55	$277.55	$277.50
Purchase #6	$131.48	10.145%	$144.8186	$144.82	$144.80	$144.80
Purchase #7	$183.33	11.610%	$204.6146	$204.61	$204.60	$204.60
7 purchase totals =	$974.82		$1,063.9521	$1,063.95	$1,063.90	$1,064.00