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	$232.41	12.175%	$260.7059	$260.71	$260.70	$260.70
Purchase #2	$177.49	7.848%	$191.4194	$191.42	$191.40	$191.40
Purchase #3	$110.58	12.735%	$124.6624	$124.66	$124.65	$124.70
Purchase #4	$192.96	11.615%	$215.3723	$215.37	$215.35	$215.40
Purchase #5	$167.77	3.767%	$174.0899	$174.09	$174.10	$174.10
Purchase #6	$76.38	9.643%	$83.7453	$83.75	$83.75	$83.70
Purchase #7	$55.64	7.641%	$59.8915	$59.89	$59.90	$59.90
7 purchase totals =	$1,013.23		$1,109.8867	$1,109.89	$1,109.85	$1,109.90