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	$163.85	8.635%	$177.9984	$178.00	$178.00	$178.00
Purchase #2	$221.90	8.837%	$241.5093	$241.51	$241.50	$241.50
Purchase #3	$216.89	10.269%	$239.1624	$239.16	$239.15	$239.20
Purchase #4	$53.59	11.840%	$59.9351	$59.94	$59.95	$59.90
Purchase #5	$137.40	9.708%	$150.7388	$150.74	$150.75	$150.70
Purchase #6	$68.50	3.352%	$70.7961	$70.80	$70.80	$70.80
Purchase #7	$201.28	10.492%	$222.3983	$222.40	$222.40	$222.40
7 purchase totals =	$1,063.41		$1,162.5384	$1,162.55	$1,162.55	$1,162.50