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	$130.87	8.603%	$142.1287	$142.13	$142.15	$142.10
Purchase #2	$212.28	10.867%	$235.3485	$235.35	$235.35	$235.30
Purchase #3	$100.26	4.659%	$104.9311	$104.93	$104.95	$104.90
Purchase #4	$225.94	5.575%	$238.5362	$238.54	$238.55	$238.50
Purchase #5	$151.58	10.843%	$168.0158	$168.02	$168.00	$168.00
Purchase #6	$245.83	6.418%	$261.6074	$261.61	$261.60	$261.60
Purchase #7	$133.62	4.671%	$139.8614	$139.86	$139.85	$139.90
7 purchase totals =	$1,200.38		$1,290.4291	$1,290.44	$1,290.45	$1,290.30