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	$245.86	10.541%	$271.7761	$271.78	$271.80	$271.80
Purchase #2	$171.67	8.112%	$185.5959	$185.60	$185.60	$185.60
Purchase #3	$39.94	3.706%	$41.4202	$41.42	$41.40	$41.40
Purchase #4	$245.60	4.267%	$256.0798	$256.08	$256.10	$256.10
Purchase #5	$30.54	10.864%	$33.8579	$33.86	$33.85	$33.90
Purchase #6	$33.91	3.778%	$35.1911	$35.19	$35.20	$35.20
Purchase #7	$33.55	9.251%	$36.6537	$36.65	$36.65	$36.70
7 purchase totals =	$801.07		$860.5747	$860.58	$860.60	$860.70