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	$31.49	5.712%	$33.2887	$33.29	$33.30	$33.30
Purchase #2	$208.89	5.873%	$221.1581	$221.16	$221.15	$221.20
Purchase #3	$136.80	13.401%	$155.1326	$155.13	$155.15	$155.10
Purchase #4	$176.54	7.490%	$189.7628	$189.76	$189.75	$189.80
Purchase #5	$151.88	12.773%	$171.2796	$171.28	$171.30	$171.30
Purchase #6	$51.47	9.326%	$56.2701	$56.27	$56.25	$56.30
Purchase #7	$160.62	10.647%	$177.7212	$177.72	$177.70	$177.70
7 purchase totals =	$917.69		$1,004.6131	$1,004.61	$1,004.60	$1,004.70