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	$47.40	11.638%	$52.9164	$52.92	$52.90	$52.90
Purchase #2	$111.67	5.145%	$117.4154	$117.42	$117.40	$117.40
Purchase #3	$126.93	5.837%	$134.3389	$134.34	$134.35	$134.30
Purchase #4	$168.79	10.201%	$186.0083	$186.01	$186.00	$186.00
Purchase #5	$80.90	10.846%	$89.6744	$89.67	$89.65	$89.70
Purchase #6	$216.53	11.633%	$241.7189	$241.72	$241.70	$241.70
Purchase #7	$135.67	5.605%	$143.2743	$143.27	$143.25	$143.30
7 purchase totals =	$887.89		$965.3466	$965.35	$965.25	$965.30