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	$200.51	5.831%	$212.2017	$212.20	$212.20	$212.20
Purchase #2	$38.63	12.657%	$43.5194	$43.52	$43.50	$43.50
Purchase #3	$40.26	8.316%	$43.608	$43.61	$43.60	$43.60
Purchase #4	$32.78	5.252%	$34.5016	$34.50	$34.50	$34.50
Purchase #5	$246.87	13.589%	$280.4172	$280.42	$280.40	$280.40
Purchase #6	$229.38	8.784%	$249.5287	$249.53	$249.55	$249.50
Purchase #7	$184.79	8.459%	$200.4214	$200.42	$200.40	$200.40
7 purchase totals =	$973.22		$1,064.1980	$1,064.20	$1,064.15	$1,064.10