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	$194.27	5.239%	$204.4478	$204.45	$204.45	$204.40
Purchase #2	$53.89	10.804%	$59.7123	$59.71	$59.70	$59.70
Purchase #3	$122.72	8.409%	$133.0395	$133.04	$133.05	$133.00
Purchase #4	$66.33	9.557%	$72.6692	$72.67	$72.65	$72.70
Purchase #5	$55.34	8.523%	$60.0566	$60.06	$60.05	$60.10
Purchase #6	$161.46	10.618%	$178.6038	$178.60	$178.60	$178.60
Purchase #7	$188.30	4.262%	$196.3253	$196.33	$196.35	$196.30
7 purchase totals =	$842.31		$904.8545	$904.86	$904.85	$904.80