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	$40.41	7.444%	$43.4181	$43.42	$43.40	$43.40
Purchase #2	$152.69	7.575%	$164.2563	$164.26	$164.25	$164.30
Purchase #3	$174.74	9.407%	$191.1778	$191.18	$191.20	$191.20
Purchase #4	$136.85	13.775%	$155.7011	$155.70	$155.70	$155.70
Purchase #5	$132.85	7.148%	$142.3461	$142.35	$142.35	$142.30
Purchase #6	$175.86	4.456%	$183.6963	$183.70	$183.70	$183.70
Purchase #7	$108.58	13.868%	$123.6379	$123.64	$123.65	$123.60
7 purchase totals =	$921.98		$1,004.2336	$1,004.25	$1,004.25	$1,004.20