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	$171.29	6.830%	$182.9891	$182.99	$183.00	$183.00
Purchase #2	$121.73	3.518%	$126.0125	$126.01	$126.00	$126.00
Purchase #3	$125.74	3.866%	$130.6011	$130.60	$130.60	$130.60
Purchase #4	$52.59	12.359%	$59.0896	$59.09	$59.10	$59.10
Purchase #5	$188.31	6.662%	$200.8552	$200.86	$200.85	$200.90
Purchase #6	$53.61	6.300%	$56.9874	$56.99	$57.00	$57.00
Purchase #7	$239.37	8.871%	$260.6045	$260.60	$260.60	$260.60
7 purchase totals =	$952.64		$1,017.1394	$1,017.14	$1,017.15	$1,017.20