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	$219.92	13.154%	$248.8483	$248.85	$248.85	$248.80
Purchase #2	$229.98	12.802%	$259.422	$259.42	$259.40	$259.40
Purchase #3	$196.30	4.156%	$204.4582	$204.46	$204.45	$204.50
Purchase #4	$9.46	3.610%	$9.8015	$9.80	$9.80	$9.80
Purchase #5	$248.93	5.487%	$262.5888	$262.59	$262.60	$262.60
Purchase #6	$53.70	11.347%	$59.7933	$59.79	$59.80	$59.80
Purchase #7	$162.74	9.289%	$177.8569	$177.86	$177.85	$177.90
7 purchase totals =	$1,121.03		$1,222.7690	$1,222.77	$1,222.75	$1,222.80