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	$184.93	11.720%	$206.6038	$206.60	$206.60	$206.60
Purchase #2	$214.42	12.859%	$241.9923	$241.99	$242.00	$242.00
Purchase #3	$69.89	11.804%	$78.1398	$78.14	$78.15	$78.10
Purchase #4	$95.38	11.178%	$106.0416	$106.04	$106.05	$106.00
Purchase #5	$136.98	5.292%	$144.229	$144.23	$144.25	$144.20
Purchase #6	$84.89	6.367%	$90.2949	$90.29	$90.30	$90.30
Purchase #7	$54.56	8.549%	$59.2243	$59.22	$59.20	$59.20
7 purchase totals =	$841.05		$926.5257	$926.51	$926.55	$926.40