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	$127.78	9.565%	$140.0022	$140.00	$140.00	$140.00
Purchase #2	$73.72	11.779%	$82.4035	$82.40	$82.40	$82.40
Purchase #3	$116.88	12.231%	$131.1756	$131.18	$131.20	$131.20
Purchase #4	$6.97	3.192%	$7.1925	$7.19	$7.20	$7.20
Purchase #5	$165.77	4.697%	$173.5562	$173.56	$173.55	$173.60
Purchase #6	$112.82	3.302%	$116.5453	$116.55	$116.55	$116.50
Purchase #7	$56.78	9.517%	$62.1838	$62.18	$62.20	$62.20
7 purchase totals =	$660.72		$713.0591	$713.06	$713.10	$713.10