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	$195.52	13.283%	$221.4909	$221.49	$221.50	$221.50
Purchase #2	$228.91	13.367%	$259.5084	$259.51	$259.50	$259.50
Purchase #3	$96.91	3.850%	$100.641	$100.64	$100.65	$100.60
Purchase #4	$108.90	5.570%	$114.9657	$114.97	$114.95	$115.00
Purchase #5	$162.41	11.397%	$180.9199	$180.92	$180.90	$180.90
Purchase #6	$217.89	11.108%	$242.0932	$242.09	$242.10	$242.10
Purchase #7	$137.37	4.247%	$143.2041	$143.20	$143.20	$143.20
7 purchase totals =	$1,147.91		$1,262.8232	$1,262.82	$1,262.80	$1,262.80