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	$214.36	6.781%	$228.8958	$228.90	$228.90	$228.90
Purchase #2	$157.65	13.701%	$179.2496	$179.25	$179.25	$179.20
Purchase #3	$6.75	13.156%	$7.638	$7.64	$7.65	$7.60
Purchase #4	$30.42	3.669%	$31.5361	$31.54	$31.55	$31.50
Purchase #5	$182.38	4.698%	$190.9482	$190.95	$190.95	$190.90
Purchase #6	$44.71	13.145%	$50.5871	$50.59	$50.60	$50.60
Purchase #7	$167.83	11.764%	$187.5735	$187.57	$187.55	$187.60
7 purchase totals =	$804.10		$876.4283	$876.44	$876.45	$876.30