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	$71.71	9.270%	$78.3575	$78.36	$78.35	$78.40
Purchase #2	$134.81	5.655%	$142.4335	$142.43	$142.45	$142.40
Purchase #3	$185.78	3.680%	$192.6167	$192.62	$192.60	$192.60
Purchase #4	$112.95	8.726%	$122.806	$122.81	$122.80	$122.80
Purchase #5	$141.68	7.324%	$152.0566	$152.06	$152.05	$152.10
Purchase #6	$198.61	5.347%	$209.2297	$209.23	$209.25	$209.20
Purchase #7	$191.25	12.445%	$215.0511	$215.05	$215.05	$215.10
7 purchase totals =	$1,036.79		$1,112.5511	$1,112.56	$1,112.55	$1,112.60