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	$224.69	9.139%	$245.2244	$245.22	$245.20	$245.20
Purchase #2	$68.95	11.742%	$77.0461	$77.05	$77.05	$77.00
Purchase #3	$228.41	12.466%	$256.8836	$256.88	$256.90	$256.90
Purchase #4	$55.80	12.801%	$62.943	$62.94	$62.95	$62.90
Purchase #5	$250.60	11.793%	$280.1533	$280.15	$280.15	$280.20
Purchase #6	$148.72	10.594%	$164.4754	$164.48	$164.50	$164.50
Purchase #7	$119.92	9.169%	$130.9155	$130.92	$130.90	$130.90
7 purchase totals =	$1,097.09		$1,217.6413	$1,217.64	$1,217.65	$1,217.60