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	$98.98	12.641%	$111.4921	$111.49	$111.50	$111.50
Purchase #2	$41.27	5.661%	$43.6063	$43.61	$43.60	$43.60
Purchase #3	$226.92	9.559%	$248.6113	$248.61	$248.60	$248.60
Purchase #4	$139.88	12.600%	$157.5049	$157.50	$157.50	$157.50
Purchase #5	$68.92	11.396%	$76.7741	$76.77	$76.75	$76.80
Purchase #6	$236.69	11.533%	$263.9875	$263.99	$264.00	$264.00
Purchase #7	$120.97	5.201%	$127.2616	$127.26	$127.25	$127.30
7 purchase totals =	$933.63		$1,029.2378	$1,029.23	$1,029.20	$1,029.30