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	$80.66	7.176%	$86.4482	$86.45	$86.45	$86.40
Purchase #2	$169.43	9.599%	$185.6936	$185.69	$185.70	$185.70
Purchase #3	$31.71	5.636%	$33.4972	$33.50	$33.50	$33.50
Purchase #4	$53.72	6.249%	$57.077	$57.08	$57.10	$57.10
Purchase #5	$189.91	10.205%	$209.2903	$209.29	$209.30	$209.30
Purchase #6	$6.64	12.155%	$7.4471	$7.45	$7.45	$7.40
Purchase #7	$67.69	4.273%	$70.5824	$70.58	$70.60	$70.60
7 purchase totals =	$599.76		$650.0358	$650.04	$650.10	$650.00