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	$131.74	10.216%	$145.1986	$145.20	$145.20	$145.20
Purchase #2	$75.95	8.798%	$82.6321	$82.63	$82.65	$82.60
Purchase #3	$98.54	4.446%	$102.9211	$102.92	$102.90	$102.90
Purchase #4	$36.27	10.544%	$40.0943	$40.09	$40.10	$40.10
Purchase #5	$65.88	11.564%	$73.4984	$73.50	$73.50	$73.50
Purchase #6	$66.46	11.851%	$74.3362	$74.34	$74.35	$74.30
Purchase #7	$97.60	6.418%	$103.864	$103.86	$103.85	$103.90
7 purchase totals =	$572.44		$622.5447	$622.54	$622.55	$622.50