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	$66.29	7.738%	$71.4195	$71.42	$71.40	$71.40
Purchase #2	$230.56	7.492%	$247.8336	$247.83	$247.85	$247.80
Purchase #3	$212.52	13.579%	$241.3781	$241.38	$241.40	$241.40
Purchase #4	$244.40	8.242%	$264.5434	$264.54	$264.55	$264.50
Purchase #5	$109.30	9.212%	$119.3687	$119.37	$119.35	$119.40
Purchase #6	$29.82	5.314%	$31.4046	$31.40	$31.40	$31.40
Purchase #7	$236.38	5.164%	$248.5867	$248.59	$248.60	$248.60
7 purchase totals =	$1,129.27		$1,224.5346	$1,224.53	$1,224.55	$1,224.50