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	$215.72	5.629%	$227.8629	$227.86	$227.85	$227.90
Purchase #2	$209.40	3.186%	$216.0715	$216.07	$216.05	$216.10
Purchase #3	$118.50	8.782%	$128.9067	$128.91	$128.90	$128.90
Purchase #4	$171.60	8.306%	$185.8531	$185.85	$185.85	$185.90
Purchase #5	$108.29	7.534%	$116.4486	$116.45	$116.45	$116.40
Purchase #6	$225.74	10.218%	$248.8061	$248.81	$248.80	$248.80
Purchase #7	$165.54	5.432%	$174.5321	$174.53	$174.55	$174.50
7 purchase totals =	$1,214.79		$1,298.4810	$1,298.48	$1,298.45	$1,298.50