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	$175.95	4.349%	$183.6021	$183.60	$183.60	$183.60
Purchase #2	$58.41	6.831%	$62.4	$62.40	$62.40	$62.40
Purchase #3	$56.53	5.267%	$59.5074	$59.51	$59.50	$59.50
Purchase #4	$249.81	12.249%	$280.4092	$280.41	$280.40	$280.40
Purchase #5	$29.66	11.761%	$33.1483	$33.15	$33.15	$33.10
Purchase #6	$165.92	6.699%	$177.035	$177.04	$177.05	$177.00
Purchase #7	$191.25	12.786%	$215.7032	$215.70	$215.70	$215.70
7 purchase totals =	$927.53		$1,011.8052	$1,011.81	$1,011.80	$1,011.70