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	$238.34	10.274%	$262.8271	$262.83	$262.85	$262.80
Purchase #2	$166.78	4.762%	$174.7221	$174.72	$174.70	$174.70
Purchase #3	$107.60	3.462%	$111.3251	$111.33	$111.35	$111.30
Purchase #4	$250.60	3.391%	$259.0978	$259.10	$259.10	$259.10
Purchase #5	$160.29	5.424%	$168.9841	$168.98	$169.00	$169.00
Purchase #6	$57.68	10.480%	$63.7249	$63.72	$63.70	$63.70
Purchase #7	$23.99	6.701%	$25.5976	$25.60	$25.60	$25.60
7 purchase totals =	$1,005.28		$1,066.2787	$1,066.28	$1,066.30	$1,066.20