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	$104.83	11.333%	$116.7104	$116.71	$116.70	$116.70
Purchase #2	$245.99	11.627%	$274.5913	$274.59	$274.60	$274.60
Purchase #3	$41.52	8.752%	$45.1538	$45.15	$45.15	$45.20
Purchase #4	$47.95	10.779%	$53.1185	$53.12	$53.10	$53.10
Purchase #5	$39.69	13.538%	$45.0632	$45.06	$45.05	$45.10
Purchase #6	$148.73	9.316%	$162.5857	$162.59	$162.60	$162.60
Purchase #7	$101.83	10.713%	$112.739	$112.74	$112.75	$112.70
7 purchase totals =	$730.54		$809.9619	$809.96	$809.95	$810.00