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	$184.45	12.160%	$206.8791	$206.88	$206.90	$206.90
Purchase #2	$232.89	13.810%	$265.0521	$265.05	$265.05	$265.10
Purchase #3	$63.83	10.184%	$70.3304	$70.33	$70.35	$70.30
Purchase #4	$156.80	5.834%	$165.9477	$165.95	$165.95	$165.90
Purchase #5	$141.35	6.778%	$150.9307	$150.93	$150.95	$150.90
Purchase #6	$164.68	12.387%	$185.0789	$185.08	$185.10	$185.10
Purchase #7	$207.50	9.545%	$227.3059	$227.31	$227.30	$227.30
7 purchase totals =	$1,151.50		$1,271.5248	$1,271.53	$1,271.60	$1,271.50