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	$172.83	4.398%	$180.4311	$180.43	$180.45	$180.40
Purchase #2	$132.82	13.378%	$150.5887	$150.59	$150.60	$150.60
Purchase #3	$51.33	8.749%	$55.8209	$55.82	$55.80	$55.80
Purchase #4	$97.35	10.340%	$107.416	$107.42	$107.40	$107.40
Purchase #5	$145.55	6.788%	$155.4299	$155.43	$155.45	$155.40
Purchase #6	$28.75	10.347%	$31.7248	$31.72	$31.70	$31.70
Purchase #7	$59.98	9.220%	$65.5102	$65.51	$65.50	$65.50
7 purchase totals =	$688.61		$746.9216	$746.92	$746.90	$746.80