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	$89.69	12.749%	$101.1246	$101.12	$101.10	$101.10
Purchase #2	$95.64	13.603%	$108.6499	$108.65	$108.65	$108.60
Purchase #3	$187.26	5.186%	$196.9713	$196.97	$196.95	$197.00
Purchase #4	$99.25	12.526%	$111.6821	$111.68	$111.70	$111.70
Purchase #5	$95.69	7.184%	$102.5644	$102.56	$102.55	$102.60
Purchase #6	$104.89	7.353%	$112.6026	$112.60	$112.60	$112.60
Purchase #7	$52.65	10.337%	$58.0924	$58.09	$58.10	$58.10
7 purchase totals =	$725.07		$791.6873	$791.67	$791.65	$791.70