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	$94.30	4.731%	$98.7613	$98.76	$98.75	$98.80
Purchase #2	$234.65	12.104%	$263.052	$263.05	$263.05	$263.10
Purchase #3	$138.95	4.256%	$144.8637	$144.86	$144.85	$144.90
Purchase #4	$100.78	5.128%	$105.948	$105.95	$105.95	$105.90
Purchase #5	$227.91	5.230%	$239.8297	$239.83	$239.85	$239.80
Purchase #6	$37.78	6.675%	$40.3018	$40.30	$40.30	$40.30
Purchase #7	$156.55	3.703%	$162.347	$162.35	$162.35	$162.30
7 purchase totals =	$990.92		$1,055.1035	$1,055.10	$1,055.10	$1,055.10