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	$139.25	9.576%	$152.5846	$152.58	$152.60	$152.60
Purchase #2	$25.70	13.765%	$29.2376	$29.24	$29.25	$29.20
Purchase #3	$88.81	12.327%	$99.7576	$99.76	$99.75	$99.80
Purchase #4	$78.91	11.601%	$88.0643	$88.06	$88.05	$88.10
Purchase #5	$15.25	13.587%	$17.322	$17.32	$17.30	$17.30
Purchase #6	$80.46	5.672%	$85.0237	$85.02	$85.00	$85.00
Purchase #7	$249.29	12.425%	$280.2643	$280.26	$280.25	$280.30
7 purchase totals =	$677.67		$752.2541	$752.24	$752.20	$752.30