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	$139.90	4.124%	$145.6695	$145.67	$145.65	$145.70
Purchase #2	$219.94	5.546%	$232.1379	$232.14	$232.15	$232.10
Purchase #3	$163.29	5.615%	$172.4587	$172.46	$172.45	$172.50
Purchase #4	$85.71	4.833%	$89.8524	$89.85	$89.85	$89.90
Purchase #5	$51.55	5.108%	$54.1832	$54.18	$54.20	$54.20
Purchase #6	$199.31	3.448%	$206.1822	$206.18	$206.20	$206.20
Purchase #7	$96.92	6.423%	$103.1452	$103.15	$103.15	$103.10
7 purchase totals =	$956.62		$1,003.6291	$1,003.63	$1,003.65	$1,003.70