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	$228.83	10.652%	$253.205	$253.21	$253.20	$253.20
Purchase #2	$153.52	11.713%	$171.5018	$171.50	$171.50	$171.50
Purchase #3	$239.96	7.712%	$258.4657	$258.47	$258.45	$258.50
Purchase #4	$98.76	4.399%	$103.1045	$103.10	$103.10	$103.10
Purchase #5	$210.87	13.578%	$239.5019	$239.50	$239.50	$239.50
Purchase #6	$205.64	10.577%	$227.3905	$227.39	$227.40	$227.40
Purchase #7	$145.41	4.106%	$151.3805	$151.38	$151.40	$151.40
7 purchase totals =	$1,282.99		$1,404.5499	$1,404.55	$1,404.55	$1,404.60