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	$140.31	9.366%	$153.4514	$153.45	$153.45	$153.50
Purchase #2	$210.34	5.289%	$221.4649	$221.46	$221.45	$221.50
Purchase #3	$192.28	3.460%	$198.9329	$198.93	$198.95	$198.90
Purchase #4	$46.59	3.758%	$48.3409	$48.34	$48.35	$48.30
Purchase #5	$6.59	8.833%	$7.1721	$7.17	$7.15	$7.20
Purchase #6	$231.65	3.322%	$239.3454	$239.35	$239.35	$239.30
Purchase #7	$177.89	10.531%	$196.6236	$196.62	$196.60	$196.60
7 purchase totals =	$1,005.65		$1,065.3312	$1,065.32	$1,065.30	$1,065.30