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	$148.50	4.691%	$155.4661	$155.47	$155.45	$155.50
Purchase #2	$209.98	12.333%	$235.8768	$235.88	$235.90	$235.90
Purchase #3	$52.71	4.726%	$55.2011	$55.20	$55.20	$55.20
Purchase #4	$176.69	12.783%	$199.2763	$199.28	$199.30	$199.30
Purchase #5	$225.26	13.576%	$255.8413	$255.84	$255.85	$255.80
Purchase #6	$98.31	5.119%	$103.3425	$103.34	$103.35	$103.30
Purchase #7	$57.34	8.509%	$62.2191	$62.22	$62.20	$62.20
7 purchase totals =	$968.79		$1,067.2232	$1,067.23	$1,067.25	$1,067.20