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	$236.53	4.702%	$247.6516	$247.65	$247.65	$247.70
Purchase #2	$64.85	3.569%	$67.1645	$67.16	$67.15	$67.20
Purchase #3	$24.77	11.418%	$27.5982	$27.60	$27.60	$27.60
Purchase #4	$55.59	13.569%	$63.133	$63.13	$63.15	$63.10
Purchase #5	$228.91	4.844%	$239.9984	$240.00	$240.00	$240.00
Purchase #6	$184.89	6.438%	$196.7932	$196.79	$196.80	$196.80
Purchase #7	$182.79	6.169%	$194.0663	$194.07	$194.05	$194.10
7 purchase totals =	$978.33		$1,036.4052	$1,036.40	$1,036.40	$1,036.50