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	$74.44	5.580%	$78.5938	$78.59	$78.60	$78.60
Purchase #2	$246.78	4.809%	$258.6477	$258.65	$258.65	$258.60
Purchase #3	$69.78	4.334%	$72.8043	$72.80	$72.80	$72.80
Purchase #4	$105.27	9.107%	$114.8569	$114.86	$114.85	$114.90
Purchase #5	$65.89	13.140%	$74.5479	$74.55	$74.55	$74.50
Purchase #6	$238.80	3.549%	$247.275	$247.28	$247.30	$247.30
Purchase #7	$139.68	10.643%	$154.5461	$154.55	$154.55	$154.50
7 purchase totals =	$940.64		$1,001.2717	$1,001.28	$1,001.30	$1,001.20