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	$216.53	13.415%	$245.5775	$245.58	$245.60	$245.60
Purchase #2	$75.31	5.509%	$79.4588	$79.46	$79.45	$79.50
Purchase #3	$177.26	6.640%	$189.0301	$189.03	$189.05	$189.00
Purchase #4	$72.64	7.189%	$77.8621	$77.86	$77.85	$77.90
Purchase #5	$159.40	5.828%	$168.6898	$168.69	$168.70	$168.70
Purchase #6	$91.58	13.326%	$103.784	$103.78	$103.80	$103.80
Purchase #7	$249.89	5.356%	$263.2741	$263.27	$263.25	$263.30
7 purchase totals =	$1,042.61		$1,127.6764	$1,127.67	$1,127.70	$1,127.80