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	$77.95	10.851%	$86.4084	$86.41	$86.40	$86.40
Purchase #2	$10.93	9.712%	$11.9915	$11.99	$12.00	$12.00
Purchase #3	$178.65	12.113%	$200.2899	$200.29	$200.30	$200.30
Purchase #4	$145.71	7.693%	$156.9195	$156.92	$156.90	$156.90
Purchase #5	$233.59	3.162%	$240.9761	$240.98	$241.00	$241.00
Purchase #6	$98.76	12.577%	$111.181	$111.18	$111.20	$111.20
Purchase #7	$199.58	6.297%	$212.1476	$212.15	$212.15	$212.10
7 purchase totals =	$945.17		$1,019.9140	$1,019.92	$1,019.95	$1,019.90