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	$167.59	11.319%	$186.5595	$186.56	$186.55	$186.60
Purchase #2	$138.38	9.188%	$151.0944	$151.09	$151.10	$151.10
Purchase #3	$217.43	3.155%	$224.2899	$224.29	$224.30	$224.30
Purchase #4	$95.28	5.187%	$100.2222	$100.22	$100.20	$100.20
Purchase #5	$76.98	10.812%	$85.3031	$85.30	$85.30	$85.30
Purchase #6	$169.57	4.841%	$177.7789	$177.78	$177.80	$177.80
Purchase #7	$212.71	5.723%	$224.8834	$224.88	$224.90	$224.90
7 purchase totals =	$1,077.94		$1,150.1314	$1,150.12	$1,150.15	$1,150.20