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	$215.78	3.127%	$222.5274	$222.53	$222.55	$222.50
Purchase #2	$211.67	12.648%	$238.442	$238.44	$238.45	$238.40
Purchase #3	$213.28	4.344%	$222.5449	$222.54	$222.55	$222.50
Purchase #4	$105.47	8.451%	$114.3833	$114.38	$114.40	$114.40
Purchase #5	$240.86	9.174%	$262.9565	$262.96	$262.95	$263.00
Purchase #6	$232.56	5.353%	$245.0089	$245.01	$245.00	$245.00
Purchase #7	$81.32	10.241%	$89.648	$89.65	$89.65	$89.60
7 purchase totals =	$1,300.94		$1,395.5110	$1,395.51	$1,395.55	$1,395.40