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	$129.78	11.777%	$145.0642	$145.06	$145.05	$145.10
Purchase #2	$90.79	11.276%	$101.0275	$101.03	$101.05	$101.00
Purchase #3	$25.28	6.851%	$27.0119	$27.01	$27.00	$27.00
Purchase #4	$151.85	9.582%	$166.4003	$166.40	$166.40	$166.40
Purchase #5	$235.99	11.624%	$263.4215	$263.42	$263.40	$263.40
Purchase #6	$143.42	10.386%	$158.3156	$158.32	$158.30	$158.30
Purchase #7	$215.40	4.578%	$225.261	$225.26	$225.25	$225.30
7 purchase totals =	$992.51		$1,086.5020	$1,086.50	$1,086.45	$1,086.50