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	$167.83	11.849%	$187.7162	$187.72	$187.70	$187.70
Purchase #2	$72.80	4.709%	$76.2282	$76.23	$76.25	$76.20
Purchase #3	$102.97	6.393%	$109.5529	$109.55	$109.55	$109.60
Purchase #4	$216.96	4.790%	$227.3524	$227.35	$227.35	$227.40
Purchase #5	$166.29	10.390%	$183.5675	$183.57	$183.55	$183.60
Purchase #6	$73.75	12.341%	$82.8515	$82.85	$82.85	$82.90
Purchase #7	$151.71	11.637%	$169.3645	$169.36	$169.35	$169.40
7 purchase totals =	$952.31		$1,036.6332	$1,036.63	$1,036.60	$1,036.80