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	$43.72	7.523%	$47.0091	$47.01	$47.00	$47.00
Purchase #2	$45.25	12.681%	$50.9882	$50.99	$51.00	$51.00
Purchase #3	$37.72	7.656%	$40.6078	$40.61	$40.60	$40.60
Purchase #4	$80.61	12.619%	$90.7822	$90.78	$90.80	$90.80
Purchase #5	$186.84	9.400%	$204.403	$204.40	$204.40	$204.40
Purchase #6	$114.31	3.656%	$118.4892	$118.49	$118.50	$118.50
Purchase #7	$191.40	10.374%	$211.2558	$211.26	$211.25	$211.30
7 purchase totals =	$699.85		$763.5353	$763.54	$763.55	$763.60