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	$124.40	3.337%	$128.5512	$128.55	$128.55	$128.60
Purchase #2	$89.60	5.641%	$94.6543	$94.65	$94.65	$94.70
Purchase #3	$216.83	5.107%	$227.9035	$227.90	$227.90	$227.90
Purchase #4	$142.77	6.141%	$151.5375	$151.54	$151.55	$151.50
Purchase #5	$157.99	6.363%	$168.0429	$168.04	$168.05	$168.00
Purchase #6	$68.49	12.858%	$77.2964	$77.30	$77.30	$77.30
Purchase #7	$219.87	4.433%	$229.6168	$229.62	$229.60	$229.60
7 purchase totals =	$1,019.95		$1,077.6026	$1,077.60	$1,077.60	$1,077.60