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	$215.89	6.233%	$229.3464	$229.35	$229.35	$229.30
Purchase #2	$40.97	6.455%	$43.6146	$43.61	$43.60	$43.60
Purchase #3	$18.87	7.377%	$20.262	$20.26	$20.25	$20.30
Purchase #4	$69.94	4.664%	$73.202	$73.20	$73.20	$73.20
Purchase #5	$49.38	5.412%	$52.0524	$52.05	$52.05	$52.10
Purchase #6	$94.32	13.245%	$106.8127	$106.81	$106.80	$106.80
Purchase #7	$71.45	12.409%	$80.3162	$80.32	$80.30	$80.30
7 purchase totals =	$560.82		$605.6063	$605.60	$605.55	$605.60