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	$134.41	6.425%	$143.0458	$143.05	$143.05	$143.00
Purchase #2	$203.75	7.698%	$219.4347	$219.43	$219.45	$219.40
Purchase #3	$85.96	5.166%	$90.4007	$90.40	$90.40	$90.40
Purchase #4	$222.72	5.779%	$235.591	$235.59	$235.60	$235.60
Purchase #5	$225.66	3.873%	$234.3998	$234.40	$234.40	$234.40
Purchase #6	$139.34	13.683%	$158.4059	$158.41	$158.40	$158.40
Purchase #7	$194.93	12.485%	$219.267	$219.27	$219.25	$219.30
7 purchase totals =	$1,206.77		$1,300.5449	$1,300.55	$1,300.55	$1,300.50