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	$91.59	10.154%	$100.89	$100.89	$100.90	$100.90
Purchase #2	$49.53	9.318%	$54.1452	$54.15	$54.15	$54.10
Purchase #3	$76.70	10.824%	$85.002	$85.00	$85.00	$85.00
Purchase #4	$11.67	12.648%	$13.146	$13.15	$13.15	$13.10
Purchase #5	$128.43	12.518%	$144.5069	$144.51	$144.50	$144.50
Purchase #6	$112.37	3.543%	$116.3513	$116.35	$116.35	$116.40
Purchase #7	$192.80	13.360%	$218.5581	$218.56	$218.55	$218.60
7 purchase totals =	$663.09		$732.5995	$732.61	$732.60	$732.60