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	$160.82	8.536%	$174.5476	$174.55	$174.55	$174.50
Purchase #2	$142.59	5.445%	$150.354	$150.35	$150.35	$150.40
Purchase #3	$80.53	10.823%	$89.2458	$89.25	$89.25	$89.20
Purchase #4	$102.58	11.570%	$114.4485	$114.45	$114.45	$114.40
Purchase #5	$147.67	7.333%	$158.4986	$158.50	$158.50	$158.50
Purchase #6	$116.63	4.743%	$122.1618	$122.16	$122.15	$122.20
Purchase #7	$241.45	13.360%	$273.7077	$273.71	$273.70	$273.70
7 purchase totals =	$992.27		$1,082.9640	$1,082.97	$1,082.95	$1,082.90