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	$132.55	13.808%	$150.8525	$150.85	$150.85	$150.90
Purchase #2	$127.32	8.444%	$138.0709	$138.07	$138.05	$138.10
Purchase #3	$48.62	7.112%	$52.0779	$52.08	$52.10	$52.10
Purchase #4	$119.53	10.607%	$132.2085	$132.21	$132.20	$132.20
Purchase #5	$83.35	10.447%	$92.0576	$92.06	$92.05	$92.10
Purchase #6	$70.28	11.178%	$78.1359	$78.14	$78.15	$78.10
Purchase #7	$191.80	11.213%	$213.3065	$213.31	$213.30	$213.30
7 purchase totals =	$773.45		$856.7098	$856.72	$856.70	$856.80