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	$59.81	9.203%	$65.3143	$65.31	$65.30	$65.30
Purchase #2	$172.90	8.507%	$187.6086	$187.61	$187.60	$187.60
Purchase #3	$203.35	12.487%	$228.7423	$228.74	$228.75	$228.70
Purchase #4	$196.40	9.788%	$215.6236	$215.62	$215.60	$215.60
Purchase #5	$101.45	10.211%	$111.8091	$111.81	$111.80	$111.80
Purchase #6	$116.49	5.767%	$123.208	$123.21	$123.20	$123.20
Purchase #7	$172.64	9.204%	$188.5298	$188.53	$188.55	$188.50
7 purchase totals =	$1,023.04		$1,120.8357	$1,120.83	$1,120.80	$1,120.70