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	$216.56	5.781%	$229.0793	$229.08	$229.10	$229.10
Purchase #2	$147.98	4.247%	$154.2647	$154.26	$154.25	$154.30
Purchase #3	$82.81	9.146%	$90.3838	$90.38	$90.40	$90.40
Purchase #4	$62.69	9.283%	$68.5095	$68.51	$68.50	$68.50
Purchase #5	$177.89	6.734%	$189.8691	$189.87	$189.85	$189.90
Purchase #6	$227.81	12.537%	$256.3705	$256.37	$256.35	$256.40
Purchase #7	$128.61	8.142%	$139.0814	$139.08	$139.10	$139.10
7 purchase totals =	$1,044.35		$1,127.5583	$1,127.55	$1,127.55	$1,127.70