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	$109.94	7.550%	$118.2405	$118.24	$118.25	$118.20
Purchase #2	$203.44	9.294%	$222.3477	$222.35	$222.35	$222.30
Purchase #3	$91.61	9.536%	$100.3459	$100.35	$100.35	$100.30
Purchase #4	$15.29	12.377%	$17.1824	$17.18	$17.20	$17.20
Purchase #5	$68.93	13.395%	$78.1632	$78.16	$78.15	$78.20
Purchase #6	$215.93	3.622%	$223.751	$223.75	$223.75	$223.80
Purchase #7	$166.31	12.801%	$187.5993	$187.60	$187.60	$187.60
7 purchase totals =	$871.45		$947.6300	$947.63	$947.65	$947.60