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	$68.71	12.154%	$77.061	$77.06	$77.05	$77.10
Purchase #2	$230.54	10.647%	$255.0856	$255.09	$255.10	$255.10
Purchase #3	$101.61	7.871%	$109.6077	$109.61	$109.60	$109.60
Purchase #4	$177.71	10.326%	$196.0603	$196.06	$196.05	$196.10
Purchase #5	$209.47	10.401%	$231.257	$231.26	$231.25	$231.30
Purchase #6	$68.43	12.870%	$77.2369	$77.24	$77.25	$77.20
Purchase #7	$60.71	8.604%	$65.9335	$65.93	$65.95	$65.90
7 purchase totals =	$917.18		$1,012.2420	$1,012.25	$1,012.25	$1,012.30